To be it isn't as black and white as that. Yeah, the translation sucks, and the GBA translation is much, much better...but the sound quality of the GBA doesn't do the game justice. So for me personally, I usually go with the fan translated ROM to get the authentic experience.
Having said that, older FF games on the PS1 never felt right. The console clearly had trouble emulating SNES games, as evident with things like distorted sound effects (Chrono Trigger) to absurd loading and saving times (Final Fantasy IV).