The GBA has extra content near/at the end of the game. I don't want to spoil it for you, so I can't say anything past that. The graphics are also a bit more spiffy looking compared to the original, but it doesn't looks VASTLY different. The game sprites are the same as in the original for example. The music quality is a little iffy, but not so bad that you would be missing out on the OST by playing this one. Don't worry about it and just have fun. If you really want to experience the game as it was meant to be without the censorship that was released with the original US version, just play the translated FFIV rom using a SNES emulator. Again, it sounds like you already have a set up, so just have fun and play.