I liked both. FF3 has better gameplay, but also is much more difficult towards the end. I didn't particularly find the plot of either to be very engaging. This was actually the fourth or fifth Final Fantasy branded title I played;
The first was Final Fantasy 1 followed by Final Fantasy Legend 1 and 2, and I forget whether ir not Final Fantasy Adventure was played before or after 2 for me.
FF1 was one of my first RPGs, it is flawed to hell and misses thing like telling how powerful a weapon is until you have it equipped (and you do the math yourself). It has its charm, and I loved the game in its original form; not the bastardized Dawn of Souls remake (which is technically better, but lacks the charm).
FF Legend 1 had a tower leading to different worlds. Characters were very simple, it took me forever to understand how to solve a riddle where a man asked for several items (battlesword is what he wanted because all items were used in battle. Yet one primitively told plot twist in this game became the most memorable in all of my videogame playing history.
FF Legend 2 was solely responsible for my interest in ancient Gods. This led me to Bulfinches Mythology among much more reading through elementary school, junior high, high school, and through my University studies. I can hardly wait to get my hands on this remake which is coming to DS.
Final Fantasy 4, it didn't have the same value to my childhood. Great music, but the most important thing to me was it pumped me for the next SNES Final Fantasy, which had appeared in magazines shortly after FF4 (Gamepro debuted the game, only it was FF5 photos), the game was delayed a year and FF6 became our next FF game. FF6 blew me away, but FF4 did not.
I was personally happier for FF3 because it was one I never officially owned. I LOVE the job system in it and the challenge. If you are like me with the history in the series I have; you'll pick FF3. Otherwise pick 4 and avoid a painful old school RPG asskicking; because FF3 is unforgiving =)
I describe myself as a little dose of toxic masculinity.