Get whatever seems best to you. The PS3 has Blu-Ray, Internet access, etc., but if you want a good multiplayer experience, there's nothing like the 360. And you might find it really hard to get used to the buttons on a PS3 when you've used the Xbox for a while (I know I did).
Of course, I'm really biased, since I've never owned any major console other than an Xbox (long live Halo/MW/Black Ops/Dead Space!).