So the Unity one is the old version. The dev working on this game was a team, and at some point the team broke up. One member of the team, TTrick, is keeping the game alive by himself but he didn't want to learn how to use Unity, so he re-coded the game using a new engine. I'm not sure what the game runs on right now, it's not renpy but might still be python based?
Anyhow, the latest version is on the new engine, the Unity version won't be getting updated anymore. Not sure how much new content there is right now though, since I think most of the dev's work was just rebuilding the game.