360 is at the limit of what it can do graphics wise now where as ps3 is just starting to get into its stride. PS3 is more expensive to buy when side by side with a 360 but to get your 360 online you then have to buy the wireless adapter for it, loads of batteries for controllers or a charge and play pack where as ps3 charges via usb.
I have both consoles and only really play my ps3 now. People say online is better on 360 but i really dont see the difference. The only reason i still have my 360 is because of forza.
Id just go to game and play both for yourself and make your mind up there as too many people are fan boys with 1 or the other console so you normally get an extremely biased view as to which to buy.
PS3 doesn't have the infinite power people seem to think it has 360 is not that far behind in terms of power and is actually stronger in some areas but the BR drive does mean PS3 is better future proofed.
Tho as said try them both get the one you like. Or alternatively if you're going to be playing with friends online get the one they have.