I asked the same question last year, I bought a PS3

of course...
PS3>Xbox
what TV do you have? one thing that you need to keep in mind that I did not know or anyone tell me is that ALOT of the PS3 games are only made at 720 and not 1080I or 1080P where as every single game I have seen for Xbox is full HD....
like Fifa 11 is only 720 which sucks as I have an LG Full HD 42" LCD... but it still looks great...
i am going to take my mates Xbox and hook it up and see who's graphics are actually better....
PS3 rocks though! Xbox have already fallen behind, PS3 is only using around 65% of its capability at the moment, so you wont have to buy a new console for years to come, Xbox are going to have to compete in the high end graphics department and will have to release a new console...
so I would get the PS3 mate. I was in the same position as you, never looked back at my choice..
plus, Xbox controllers use batteries (cost cash) PS3 uses USB to charge