I think the best version would be on the GBA
FFI&II Dawn of Souls
I know there's a PSP version, but you get BOTH games for the price of a GBA game..
and the PSP version add pretty much nothing new, it's just a port of the GBA version with some minor extras
but I would tell you to get Dawn of Souls...I really LOVED it
FFIII and FFI are my favourite games in the series, because of the lack of cinematics and the open world







