Renpy allows for easier community mods. You can compress the game, or modify it to run on Android which is usually not possible using Unity. You can create fan-based walkthroughs, galleries, or even give people the option to remove certain scenes with renpy.Well, good luck with that. Since the game has been finished for 5 years. If I may ask, what is wrong with the Unity engine, other than the obvious known differences, or "I don't play Unity games cause I hate this" ?
That said, it would be a lot of work to port this game over with little payoff. If this game were not widely available anymore, it might make sense to build a renpy version, but the game is available on Steam and here, so there isn't much reason to do that.