As said, it kind of depends on what you are looking for?
I have a PS3, and Wii, and borrowed an Xbox for quite awhile.
PS3 gets my vote. Free internet gaming, if that's what you want. The PSN was hacked but as far as I know the security features were greatly enhanced.
If you get a PS3 exclusive game you will notice the difference in power. (I highly recommend the Drake Uncharted Series, AMAZING and fun, as well as Gran turismo 5 of course. PS, get a racing wheel for any racing games, best investment ever.) An Xbox-PS3 game often gets limited to what the Xbox can do since it has less ability to produce the graphics etc PS3 can.
As for Xbox having more games, I don't buy it. If it is, it's negligible. I haven’t really found myself ever saying, “Man I really wish I had an Xbox cause I can’t find a game to play”.
Xbox Kinect does seem to beat the PS3’s motion system though. But I haven’t really played much with those gimmicks yet. I’m waiting to see if it really becomes better than what they have now. They are still somewhat in their infancy.
But, as one poster mentioned, go to Best Buy or something, try them all and see. They will be your best bet.