I have a 360, I love it.
Both machines get some great exclusives, I happen to prefer the 360's (Mass Effect, Gears of War) but the PS3 gets some good exclusive content as well.
Honestly, the two things I would consider would be the controllers. I personally would take a 360 controller over a PS controller any day of the goddamn week.
And what about BluRay? If you get a PS3 you suddenly have access to BluRay DVDs. It's something to consider.
If it's just about gaming, I can't speak for the PS3, I can only tell you that I am 100% satisfied with my Xbox 360 purchase.