The original Seiken Densetsu 3 was one of the best of the series. It had multiplayer for online coop, it had good character choices, it had good development of skills, and it was both pretty and fun at the same time. It's the game I played the most of using ZSNES netplay.

The remake, Trials of Mana, is fascinating. The main thing about it is that it's a really good game as well, but plays nothing alike. It's actually a proper remake, as in, everything is changed enough to warrant calling it a remake, yet it's similar enough to be the same game. Being a really good game makes it good in it's own right, but it also doesn't invalidate playing the original as Seiken Densetsu 3 is a different kind of game that is also really good.

Trials of Mana is the golden standard because it resulted in two really good games where you can play both and have a great time. It's fair to like one over the other due to preferring that style of game or art more, but they are factually both great games.