The Playstation 1 version is available on the Playstation Network and on Xbox Live Arcade. The XBLA version has Graphics smoothing, multiple leaderboards for speed runs, score, etc, and of course Achievements. If you create a Japanese account, you can also get the Japanese version of the game. I have both on my Xbox 360. The Japanese version has the extra familiars, and the extra items. That leaves the two exclusive added areas as the only things besides playable Maria that the Saturn version has. Everything I've ever read states that those areas are odd and don't fit the overall theme of the game well anyway.
It was never enough to make me track down and buy the Saturn version, but maybe I will one of these days just for the sake of trying it once.
However, if you just want to experience the game, the XBLA downloadable version is probably the best overall version of the game.