The ps3 will have more units sold, because
1 The game has been announced and in development since before the ps3s launch. If people bought a console for the game then they most likely bought a ps3.
2 Japan competes with NA as the most popular region for final fantasy games. Japan is very important, and the game not being released in Japan for the 360 means that the ps3 will probably have millions of more sales.
3 Multiplatform owners, like myself, would probably buy the ps3 version just because there is less discs.
I would say the 360 would sell a good number of copies though, but not anywhere close to the number of copies sold for the PS3.







