Look for the exclusives on the ps3 and the xbox360 check out the prices of the consoles and specially with the 360 check out the real costs, because you will not get wifi or live for free and thats a given on the ps3 so check the price for the hardware the games that each console has and make an informed decision.
So far I had a 360 and moved to a ps3 for several reasons, the biggest issue for me was RROD I couldnt stand knowing some day my console would break and not play when I want or maybe having to buy a new 360, second thing was the noise the xbox 360 makes is unbelievable its like listening to a helicopter a couple of miles away and that drives me mad being an apple user.
Third and less importantly was paying for live, I never felt encouraged to pay for live never and with the ps3 you just buy it and the same day you are playing with your friends online. Another thing see what console your friends have if everyone has a 360 buy a 360 playing with friends online is unmatchable its just great, if you dont have any friends with consoles buy a ps3.
I really depends on you really, both machines are great each in a way and it all depends on what you want, which games and how you want to play them. Sony a year ago was lacking in games badly, and I mean badly, but over the course of 2008 sony has done an incredible job catching up and even growing on its own.