I have played the game on both consoles, and i don't think there is the biggest difference. Personally i like the PS3 best, because i don't want to pay to get online... what i think is the only thing bad about it is that it lags a little on both systems... oh, i was suppose to talk about the game, sorry.
When the game started for the first time and the intro starts, i thought that the game was amazing. When i played a little, i could confirm that. When i played the online mode for the first time, there was no update that could make you join another game without loading back to the off line game again, but that was fixed fast. There was a lot of players that created a game, waited for people to join and then quit, so everybody was kicked back to off line. When you kill in online mode, you get money, which you use to level up and get more clothes and characters. In the start, i thought that was amazing, but later it got just a little bit boring. Well, let's get back to off line game play. The first couple of missions is a little bit empty of action, but later you get some good and action-packed missions. I also like the story about Niko and his past. You get a bit of it all the time and i think that it's good.
I think the game is good, bit i don't think it's a game you want to complete multiple times.
My rating is:
Game play and story: 10/10
Online game play: 5/10
Graphical: 8/10
Sounds and voices: 10/10
My overall rating: 9/10