So I have 1600 MS points, which by my (albeit terrible) math will get me 2 DLC packs, one will be taken by the Arrival. I can't choose a second one, the most important factor to my decision is how much a DLC pack will effect Mass Effect 3. I know there probably isn't any solid evidence on which content will affect ME3 (and to what degree), but base it off of speculation. If Kasumi returns, thats another party member in ME3. 
 
 
 
 ****SPOILERS**** 

You get most bang for your buck by purchasing the Shadow Broker DLC, but my favorite was the Overlord DLC.  Seeing as you want to base your purchase on the effects it will have on ME3 then I would suggest getting the Shadow Broker DLC as I would imagine it would play some role in ME3.

None of us know what will happen with Liara in ME3 if you don't play the Shadow Broker. 
 
That said, I'd go with Shadow Broker but I'd totally avoid The Arrival. That DLC is trash compared to the others and probably nothing will change in ME3 if you don't play it.

Lair of the Shadow Broker is a must , is the best DLC by Bioware ever .... and Kasumi's dlc  is cool too but Shadow is a must dude

Last I heard the ending in Lair is canon for ME3 whether you buy it or not, but it was the funnest of the dlc for me but I haven't bought overlord yet.

Shadow Broker is a must, but I doubt that any of the DLC will port decisions over. Unless they've already confirmed this.

I doubt any of the DLCs will affect your ME3 game in any way. At least not more than dialogue strings that might get locked out if you didn't play them. The only DLC that could change something in ME3, would be Overlord. None of the other have any future determine choices.

But Lair of the Shadow Broker is the must in my opinion. It's the one that feels closest to Shepard, even if you didn't romance Liara. Kasumi is good because she's a nice party member, and it's quite a fun piece to play even if the combat pieces are pretty boring.

If anything, I'd say avoid Arrival and watch it on Youtube, because you have NO choices and you're alone. Kasumi and the Shadow Broker would be the two, with Shadow Broker being my definite recommendation if you prefer story over an extra squad member.

1. Shadow Broker
2. Kasumi
3.  Arrival
4. Overlord

1. Shadow Broker
2. Kasumi
3.  Arrival
4. Overlord

@SethPhotopoulos

1. Shadow Broker
2. Kasumi
3.  Arrival
4. Overlord

I'd switch arrival with overlord, the ending of overlord was really cool

@SethPhotopoulos said:

@Dany said:

@SethPhotopoulos

1. Shadow Broker
2. Kasumi
3. Arrival
4. Overlord

I'd switch arrival with overlord, the ending of overlord was really cool

I agree the ending of Overlord was great but I could not stand the rest of it.

I would have switched Arrival and Overlord, as well. But more because Arrival didn't actually give you anything.

Shadow Broker gave you closure with Liara.

Kasumi gave you a party member and a weapon.

Overlord gave you a choice.

Arrival gave you... Admiral Hackett's face?

I don't know. Just felt like I could have watched a couple of cutscenes instead because I could do nothing to affect the outcome (without going into too much details with risk of spoiling it).

Then again, I would probably still recommend Arrival over Overlord, simply because it explains something important to the story, while Overlord is just a more complex "uncharted planet mission". Something completely irrelevant to the overarching story. Would have taken a reunion with Ashley/Kaidan-DLC over Overlord any day.

Arrival is the only DLC I'd avoid if it meant sacrificing getting one of the others.

Shadow Broker is probably the more important of the lot. 

Arrival is the only Mass Effect 2 DLC I never got around to purchasing, mostly because everyone says it's 90 minutes of solo shepard just shooting things. Of course, I was also considering going for a full S Rank achievement-wise this summer so I'll probably get it eventually anyways, despite probably being garbage. Shadow Broker is obviously the one they put the most effort into, whereas Kasumi is at least decently interesting. I wasn't a huge fan of overlord, mostly because I don't think the hovertank is really that interesting.

1. Shadow Broker 2. Kasumi 3.  Arrival 4. Overlord