All in all, you can't go "wrong" with either choice. Both of them are quality consoles with many many games (80% of all games are multi-platform) so for the most part a you get the most games either way you go.
PS3 has by far the higher number of exclusive titles (PS3 only games), 360 has the better online, but have to pay for it. 360 also, in my opinion, has a better controller. It's more comfortable.
I'd just get whichever you like, but if I were you I'd look up games like God of War, Infamous, Resistance, Metal Gear, Uncharted (PS3 only games) and Gears of War, Halo, Forza, Crackdown (360 games) and others to see which set of games interest you the most, then go from there.