I hear the textures on the PS3 are sharper, but there's been report that the PS3 has framerate issues (like it does quite often).
The water seems to look a bit more realistic for the PS3, and has a bit of murkyness. Like someone kicked up some dirt at the bottom of the water, but for some reason, I like the look of the XBOX 360's water.
Let me know what everyone thinks. I would love to hear everyone's opinion. Regardless whichever system you play on, they both look amazing.