Ok. I'm about to get out of school in a month and a half and I want to play one of the Persona games over the summer break. Should I get Persona 3 or 4 or both? I'm not really looking for a dark game. I want one that will make me smile more than freak me out. 
 
Advice?

Make you smile? Not sure Persona 3 is for you then... I mean sure there are funny parts and comic relief characters but that game is pretty dark... 
 
That said, I totally suggest both.

Persona 4 is a happier story all round. But you should buy Persona 3 and then spend the rest of your time watching the Endurance Run.

I'd say if you have have the money go for both. If not buy 4.

P4 is the better game, but P3 has a better story, even if it is a darker story.

Just get and play both, you won't regret it. Just play 3 first so you don't miss the game mechanics 4 adds. I love them both and couldn't pick one over the other. You'll never get a concensus about which game has a better story, many say that both have predictable stories (who cares?), but most will just choose one or the other but it's always a close race! I'd go with 3, but that could just be because I played it first.

I'd suggest playing both, eventually. If you go with that plan, you should start with Persona 3 so you can appreciate the changes to the fighting mechanics between games (it's probably a lot more frustrating going from Persona 4 back to Persona 3).  P3 has a much more depressing tone, especially in the last 1/3 or so of the game, but then, P4 is about catching a serial killer, and thus obviously leads to some really dark places.
 
Play one this summer, then find the time to play the other some other time. It's going to be awhile before Persona 5 hits, so take your time.

Buy P3P for your PSP and Persona 4 for your PS2

both and then when your done those  GO GET PERSONA 5!!!!!

P4. I've played way more of 3 and enjoyed it quite a bit, but 4 definitely seems like the 'better' game.

Both

mk, thanks guys.