FFIV was great back in the day and all, but it's aged pretty horribly. Then again, that might just because the last time i played it was the remake, and I really hate it when game speed is unnecessarily slow. It's my biggest pet peeve with better graphics in games (Especially turn-based RPGs), because they force you to sit through characters walking and swinging their sword for 5 seconds apiece when in the good ol' days it took like 1 second.
So yeah, personally I'd play the original SNES version, difficulty purists be damned. The playstation version has awful load times and the DS has the aforementioned hair-tearing game speed.