nintendo_fanboy on 08 July 2007
I don't know how good the two versions will do compared to each other, but I'm pretty sure that the 360 game will move more hardware.
You have to remember that the GTA-crowd are the casual gamers of last generation. Not the casuals that Nintendo is going after at the moment, but male teens that want to play action games and such stuff, but they don't read reviews, don't finish games etc.
Those people most likely haven't bought one of the HD-consoles yet, but GTA is a must-have for them and therefore they're buying one now. This will probably be the 360 because its lower price and the better library, especially in the action sector.
I even predict that GTA 4 will be moving more hardware than Halo 3.
