The Chronicles Version is the closest to the original version of the game. It obviously has some minor tweaks not in the original (Quicksave, run button, FMVs) but is the closest to the original Super Famicom version in terms of difficulty and gameplay. I still consider the Chronicles version to be the best version gameplay wise though the GBA and DS are a toss up in concern of translation.

The GBA title is said to have one of the most faithful scripts to the original but it nerfs the difficulty so it can utilize the party swap feature in the end of the game. The DS version is also considered one of the most challenging entries but its difficulty is completely revamped for old school players and to compensate for the new Augment system. Hope this helps.