There's quite a big difference in both games. Namely, the difficulty.
The PS3 version got an "expansion" because the PS3 can handle more memory and space related issues that the 360 had. As a result, two bonus dungeons were made. Also, two new playable characters were added to the game.
I remember reading something about the 360 version being too easy to the point where you basically glide through the entire game. They upp'ed the difficulty in the PS3 version by increasing the health of all enemies fairly drastically and (I think) making the enemy AI a bit smarter about what they were doing.