I have an Xbox 360 and a Playstation 3. I tend to play my Xbox more, not only because more of my friends have it, but because I personally find the games/online a lot more fun. Playstation 3 is definitely something though, very impressive. Although you will find games that PS3 has that the 360 doesn't and vice-versa, PS3 doesn't have the big games I like for ex: Halo 3, Gears of war, Fable 2(when nobody is online), Left 4 Dead(?). It does however share some good ones, like CoD, Fallout 3, GTA IV, and Bioshock. Along with some of it's own like Kill Zone, Ghost Recon(I think), and Little Big Planet etc.
As far as graphics goes, neither one is significantly better than the other to make or break a decision on which to pick. At least it shouldn't matter for both of them are good. Not to mention if you have been itching to switch to Blue-ray then that is a plus for PS3.
All in all, I can give you my experience with each, and Xbox 360 has a longer lasting appeal to me. So with that I would recommend whichever your friends (if you plan playing online, if not then I don't know) have so you can play with them.