Both games I finished my first playthrough as a saint in 65-ish hours, and I'm ultimately satisfied by the long long journey both the lone wanderer and the courier went through. Aside from a lot of bugs and A F*CKING LOAD OF BUGS, however, I could hardly come up with a conclusion of which was the better experience for me. I could only say, both games are very different despite looking exactly the same. Many say FO3 was darker in general, but I'd say NV was dark in the same way that the world is overrun by ignorance, greed, primitive instincts. Slavery, rape, banditry are common themes in both games.  

The Map
Both worlds are so vastly different it's hard to compare. FO3's map is a square n times n size map. 1/4 of the map is an urban labyrinth that feels like a battlefield, but otherwise, the other 3/4 is a... wasteland. Being dumped in the square middle made me feel lost. NV's map is a long strip, but how everything is placed it feels linear at first and that you feel like you're ultimately working towards your revenge in New Vegas, as you trek through the desert and stopping by small town settlements. Coming back to the starter area to pwn some Cazzadores and Deathclaws sure felt good.

The Settlements
Don't get me wrong, every settlement in NV has its special touch, but pales in comparison with the whacky and creative ones of  FO3. The independent community of Nellis in NV reminded me of Dave's Republic in FO3. And I have to say, the Republic was much more interesting to explore. Little Lamplight, Megaton, Tenpenny Tower, Rivet city all are great vistas and diverse culturally. It's always a delight to come by these settlements and say hi to the weird fanatics who live in them.

The "Dungeons"
I guess this is the reason why some people say FO3 is darker. The dungeons. I can't recall any place in NV that truly gave me the creeps, but I have to say, i constantly jumped my chair and shat my pants while playing FO3. As cheerfully unserious the settlements are, anywhere else in the DC Wasteland is outright scary. You remember the raider super market? The hotel ruins or the metro downtown? The city of deathclaws? The super mutant vault? Or the horrors of the Dunwich building? Every time i crawled through these i was constantly praying that i'd get out as soon as possible, and fuck the loot, I'm out. I can't say it's not an overkill with blood and intestines splattered everywhere, but man, it's desolate alright. On the otherhand. the dungeons in NV... feel like dungeons. In the end of each cave or abandoned office building you fight a legendary monster and get some sweet loot. Well at least the loot isn't randomized, but they don't hold the same impact as they did in FO3.

The Factions
 I would say the scope of NV was much greater, with large factions struggling for power and ideals that ware morally ambiguous. You could feel the tension both inside the Strip with families having internal problems and the external factions eyeing on the glamorous city. Then comes my internal debate of... what would be the best for the wasteland? A NCR-ruled Vegas, or an independent one? Taxes, elites or total anarchy? Even talking to Caesar reveals he believes he's instilling "civilization" into the world, which oddly enough that as savage as the legion are, it's exactly how the "greatest ancient civilization that existed" worked. There is no good or bad in New Vegas. FO3 on the other hand, presents an obvious black and white. The Brotherhood are the knights in shining armor (which is probably why the FO fanboys would cry Bethesda killed their beloved). You could be a jerk, but you couldn't be villainous. You have to help the brotherhood to move the story onwards, and the only real moral decision is in the end. And it's a no-brainer too. Save the world, or screw it over.

The Interactions with NPCs
In NV, the first skill I maxed was Speech, because I know everyone would just bow to me when i convince them. With a speech check, I could convince people to let me go into their houses and rob them dry, have some free sex and booze. FO3, if i recall correctly, was more of a dice roll; even with 100 speech, you'd still have a chance of failing the end speech check. What I noticed was, NV had other skill checks other than speech that open up more options. Barter seems to actually be useful, as many rewards can be boosted with that. I'd say both games have their flaws in this aspect.

The Characters
Okay, I remember Dad, and maybe Fawkes, but seriously, the characters aren't that interesting. The settlements are interesting, but never was there a character that stuck out. NV had people with their own history, concerns and goals. I mean, Veronica. That's about as much proof you need to say NV had better characters.

The Attention to Detail
I can't but notice this. As said before, dungeons in NV felt like dungeons not without a reason. Almost all places i go to in FO3 has a terminal or note of some sort, with a story behind the place. So even if i go through the same models and textures, I at least feel like I'm in a different place. There's one thing about NV though, they outright cut out a lot of dungeons so I guess it's not that bad.

I have to say however, both games are very worth playing. Both worlds are worth exploring, both adventures worth living. The general feeling of FO3 was a desperate struggle to survive, a very post-apocalyptic man vs nature and man-made horrors vibe. NV was more man vs. man.  And, Veronica. I mean, come on.

TL;DR: How different were the experiences for you?

I also love them both, but I prefer FO3. New Vegas is great, but FO3 has that "something" in that urban atmosphere that NV can't imitate. I prefer exploring the ruins of a city than walking around the desert.

I was sorely disappointed that I couldn't use an old nuke to blow up anything in NV.  The new melee weapons were nice, though.  And the ending options I enjoyed more. 

I liked the writing on Vegas, the story was slightly better than 3, however that was the only thing I liked about it. 

From the get-go I thought New Vegas was the better game. The crippling caching issues (where the game would load forever if you were playing it for a long stretch) really hindered it for me, but ignoring all the technical issues it was the better game.

It took a lot of time for me to come to a decision; but I do prefer Fallout 3. New Vegas did a number of things better, like well thought out factions in the main storyline and interesting characters - especially the companions. NV also added interesting new mechanics, like skill checks during dialogue but it also had a number of good ideas that were poorly implemented. The endings for example, seem quite well thought out and branching, but having done them all they end up a little bland. You can have an impact on the places you visit, but only to an extent and in the end regardless of the faction you side with you get Ron Perlman telling you that the Wasteland is much the same as when you started. Every ending is so firmly placed in a gray area that you feel like no matter what you choose you end up with a really mixed result. Even trying to rule Vegas independently pans out pretty poorly - in FO3 I really enjoyed being able to be an magnanimous force for good in a really bad world and it seems the Mojave remains a pretty shitty place no matter what you do. 

I'd rather play a Black Isle/Troika/Obsidian game than a Bethesda game any day, but I had a lot of issues with New Vegas and just quit playing after a while. It is the better game, but I guess I'd just had too much Fallout 3 already. I also missed the VR missions from Fallout 3 and Vegas had a lot of annoying invisible walls in the environment. Both were infuriatingly buggy, but the ones in New Vegas kept really screwing me. I had to turn off all of the autosave options because it would do things like spawn my companion at the other end of a cave and then save as I heard them being mauled by fire geckos in the distance. The biggest mistake Obsidian made was that it never really made me feel like getting revenge so I had no real incentive to follow the main quest. Another problem is that the bad factions, at least Ceaser's Legion and the Powder Gangers were so damn obnoxious that I never would have even thought of making friends with them. 

I played through them both and really enjoyed both games. but I def preferred FO3! I'm not one for replaying a game (unless its a classic SNES title... i just can't help myself!) but I do find myself thinking about going for another play through of FO3... I just loved it so much!

Wow I'm surprised most of you who came here actually liked FO3 more than NV, which was unexpected as I thought most of the GB community preferred the latter.

@JoeyRavn: 
I definitely agree. Watching Rage's ghost city trailer only reminded me of how amazing the DC ruins were. Rage even has its own behemoth lurking in the city :P The thing I DIDN'T like about the ruins is the fucking metro system. It's a huge maze with rubble blocking every street and the map and map marker are not helping at all.

@Getz: 
The scenery in NV is more eye appealing and worth going out to look for. But I think all the ammo types and crafting are, as Jeff said, very peripheral and I never even touched them. It is a great idea, but in the grand scheme of things it seems like it's something that would be easily overlooked, and requires some dedication as it makes little difference to the overall gameplay experience. I think if the game had "damage numbers" popping out of enemies' heads when you hit them would much better show the effects of your customization, but otherwise, I see no difference in using armor piercing rounds and shooting the guy a few more times.

But I definitely agree the bugs are killer -- I can't even play a game for a second without fearing crashes and save corruption. Crashes are alright, at least the load times weren't as long as it is on consoles, but save corruption is a bitch. I usually spam my quicksave button in these games, and hence i lost a lot of process if it were to be corrupted. In my 65 hour game, at least 4 saves were  corrupted, and a lot of time spent trying to figure out at which point did the game start screwing up. That totally pulled me out of this otherwise phenomenal game.

@WalkerTR77: 
I like how you used Caesar's favourite word antithesis, and I can't but agree to most of your points raised. I do like the depressing endings though that you couldn't save the world without sacrificing the good, even if the world itself was never as desolate and in need of saving as the FO3 world. On the other hand, most other design decisions are not great. The perk system limits the gameplay possibilities.. I barely have the time to go through the game twice to see everything, and I swear there are more than enough perks to get you to lv 30. (heck, they BALANCED the grim reaper's sprint... there's no point in having it now) The weapon customization, as i wrote above, is ultimately unnecessary.

btw, there's at least 2 fat-mans i came across. I remember one being in the Deathclaw den in the large mining place. I do believe they took out the Rock-it-launcher, which was pretty ridiculous in FO3. I think part of the beauty of FO3 is that there's always a weird sense of humour in a dark gritty wasteland.

Anecdotal, but I had way more bugs with Fallout 3 and the side stuff was completely boring. FNV, the only really annoying bugged out part for me was the cannbal mission, which was fucked the whole way through. The characters were way more interesting. The bottleneck at the end was a bummer but that's to be expected with modern fad "choice games".

I think New Vegas had much better minute to minute gameplay....the improvements to combat and to companions were very very welcome. And the faction/disguise system was a lot of fun to play with.  But Fallout 3 had a far more personal story and a much more finely crafted adventure. The Capitol Wasteland felt far more alive and charming. And it always kinda felt like home. And for the record...anytime you level up and don't get a perk...feels just awful...

I enjoyed the Mojave Wasteland a lot more than the Capital Wasteland.

@Getz: 
The scenery in NV is more eye appealing and worth going out to look for. But I think all the ammo types and crafting are, as Jeff said, very peripheral and I never even touched them. It is a great idea, but in the grand scheme of things it seems like it's something that would be easily overlooked, and requires some dedication as it makes little difference to the overall gameplay experience. I think if the game had "damage numbers" popping out of enemies' heads when you hit them would much better show the effects of your customization, but otherwise, I see no difference in using armor piercing rounds and shooting the guy a few more times.

But I definitely agree the bugs are killer -- I can't even play a game for a second without fearing crashes and save corruption. Crashes are alright, at least the load times weren't as long as it is on consoles, but save corruption is a bitch. I usually spam my quicksave button in these games, and hence i lost a lot of process if it were to be corrupted. In my 65 hour game, at least 4 saves were  corrupted, and a lot of time spent trying to figure out at which point did the game start screwing up. That totally pulled me out of this otherwise phenomenal game.

I need to play more of New Vegas to really comment, but from what I've played, I think I would agree with your statements.

New Vegas, far and away, has better characters and stories than Fallout 3 did (Moira, Button, and Fawkes were really the only characters I latched onto). This alone validates it as a better experience for me. I still love Fallout 3, and there are a lot of great moments, but too much of that game is based around menial collection and not enough about the terrible and weird things that happen in the wasteland. I wanted more scenarios like Andale, Tenpenny Tower, and Stealing Independence. New Vegas fills many of those gaps for me. Shame Bethesda locked Harold into DC.

I agree on the whole companion thing for sure. I found Rose of Sharon Cassidy to be way more interesting than all the FO3 companions combined. 

I agree on the whole companion thing for sure. I found Rose of Sharon Cassidy to be way more interesting than all the FO3 companions combined. 

But, I also think the world in FO3 was better, New vegas felt disconnected from the vegas we all know, but The Capital Wasteland reminded me of the actual city, visiting a subway staion in DC after playing that game sent chills up my spine, and the locations in it stuck with me even more than those in New Vegas, for example, the Vault where the muscians all went mad, or where the hallucinogenic gas was released, were disturbing and interesting to explore. 

Also, you should add the fact that the weapons in New vegas are way more interesting and diverse. 

More like this dogs dookie vs that dogs dookie. its still dookie.

I like Fallout 3 more mostly on the fact that it was new to me at the time, New Vegas felt like most sequels do and didn't have that fresh new gaming experience.

I enjoy the gameplay upgrades & story/setting in NV a lot better than what was in Fallout3. That being said I thought that the DLC for Fallout3 was pretty good & enjoyed most of it as well as having the ability to play past the ending. NV though is quite buggy as hell still & quite vexed at having 2 characters save files locked as well as issues with the game's ongoing annoyance at locking up just about once every few hours if that. Hope that the DLC has patches to fix this as I'd love to be able to finish the last remaining ending off without having to save every 5 minutes or have multiple saves to try to keep away from having to start over from scratch.

 do bottle caps have weight in hardcore?

I had an awesome time with Fallout 3. One of my favorite gaming experiences. 

Fallout 3 had me more invested. Leveling up made you feel powerful instead of New Vegas where you got half the perks (DLC leveling is cool though). Quests were more extravagant. Reilly's Rangers, Oasis, Wasteland survival Guide, You gotta shoot em' in the Head, were all great. Liberty Prime would beat the living crap out of the Boomers in terms of Bad Assery. The Main storyline in 3 also made me think more of "what should I do?" Instead of "How do I get the good ending?" In my opinion the Courier wasn't as invested in the Mojave (nor it with him) as the Capital Wasteland was with The Lone Wanderer.

I loved both games, but I felt that New Vegas scratched more of my RPG itch then Fallout 3. For one, I liked the setting of New Vegas better then Fallout 3. One of the many things I liked about 3 was that I felt like I was exploring an unknown world because you start out in the security of the vault. NV, while you did explore, felt more like a known quantity to me. That being said, I loved both games but I enjoyed NV a little more. Also as a side note, I only experienced one bad glitch where the quest target fell through the world... All I had to do is reload a couple of times and he eventually did not fall through...

I'd be interested to know if any of you who preferred Fallout 3 were fans of the first two?  I loved 3, but New Vegas felt more like a Fallout game, NV just had that feel to it that Bethesda didn't really capture.

NV really improved on the voice acting and story, the struggle over deciding which faction to support made it much more engaging but somehow Fallout 3 managed to keep me hooked for longer and I don't understand why. I have had so many run throughs and saves on it that I'm scared to see how many hours have been 'wasted', whereas NV only has a normal and a hardcore save. 

I could get to the end of FO3 without my save imploding, that makes it better. 

New Vegas was better for me, personally. 

I really got into Fallout 3 due to its setting and how the world was conceived.  New Vegas had more interesting characters and story (to some degree), but as a game I found it to be really boring to play.