I found this article today and thought it was pretty good comparison graphics wise for the two systems. Made me glad I got a 360 over a ps3. And not just for the multiplayer, but now for the graphics too!
http://play.tm/wire/click/1914946 click on the compared 8 games link in the first paragraph
http://play.tm/wire/click/1914946 click on the compared 8 games link in the first paragraph