I actually bought SuperS back "in the day", as an import game. Broke the tabs on my SNES, and I still have the game today. When I got a chance to play Sailor Moon S, I said, "Wait, haven't I played this game before?" Take a look. Both games are Street Fighter type, that is, one on one battles with the scounts.
On the right, you'll see Sailor Moon S, and on the left, Sailor Moon SuperS.

Ok, I can see some similarities, let's start playing. I'll pick Sailor Moon as my character. In both games, the first challenge is Mars.

And now we fight!

Okaaaaay.... if you look, both games feature almost the exact same graphics! The only thing that's really changed is Sailor moon!

Here I've lost both times.
The nice thing about superS is the extra characters, but that's it! I think they used the same code, almost the some graphics, and called it a new game! So, if you see both for sale someplace, just get SuperS, you'll be glad you did. Oh, and I have some codes for supers. It's not much, but it's the best I can do.