I would opt for a PS3... Too many bad experiences with 360 ranging from faulty controllers (multiple times, right out the box) Playing online at a cost, RRoD, E-74, and AA battery powered controllers. Also, the directional pad is not ideal for fighters.
The only issues I've had out of my PS3 is system freezing, which, is at fault of glitchy games, not the system itself, the internet browser, and the R2 buttons give me a headache sometimes... I got trigger buttons for it the other day, and they don't work well with fighters, but, excellent for shooters, and Uncharted 2. I may have to get used to them for Marvel Vs. Capcom 2, because the thing scratched skin off of my middle finger when trying to press R1, and R2 at the same time in rapid succession, and going back and fourth between only pushing R1, or R2, and my middle finger scrapped the bottom of it.
The biggest issue I have with the 360 is the DVD discs... Think about it: 16 GB, or 50, soon to be 67... All the game's you're going to want to play are coming to PS3 anyway... There's plenty of shooters, and Uncharted 2 has modes that make it very similar to Gears of War... Alan Wake?... I don't see what the big deal is about that game, to be honest, but, then again, I don't even see what the deal is with God of War III... Just leave me alone and let me play My Uncharted 2, and Marvel Vs. Capcom 2.
Oh, and the PS3 allows you to do more stuff you probably will never need to do... Like... Connect 7 controllers at a single time to a single system. And, depending on your set up, you can have optical out sound, and HDMI, 360 wont let you do both, just one or the other.
If you decide to get a PS3, get uncharted, and maybe a couple of other games... Metal Gear Solid 4 is cheap now... I recommend playing one 1st, then the other, or the controls are going to bug you