Looking at it blind -- like for a new game I would say RenPy But there are also very good RPGM and Unity games. The problem is that some RPGM games are an endless grindfest map based nightmare where you get lost a LOT. And some Unity games are nearly unplayable. There is simply more chance of a RenPy game being a goodie. One of m,y favorites (the Spellbook) is Unity and another (The Office Wife) is RPGM
I can't recall wich game it was, but I think I saw one that had it, but it was a bit restrictive in comparison to ren'py (like, couldn't rollback past choices and such)
Generally speaking, Ren'py, as I prefer VNs, and that's what Ren'Py does well. I actively dislike RPGM and QSP, even though I play a fair amount of RPGM for some more niche genres (due to a lack of options). HTML, Unity, Unreal can all be good, but I'm under the impression that they're often not executed well, or development takes a long time due to the engines being a bit more complex (not applicable to HTML, except for the few devs delving into Snowman for Twine).
Renpy if the developer has no aspirations to actually get better at coding. The easy of modding it by even rookie coders, makes it superior to other options.
I've seen too many "devs" choose an engine that adds nothing new compared to renpy equivalents in the name of improving their skills but then proceeds to make zero improvement for years on end.
Unless you're doing something pretty advanced, Unity and the like are complete overkill for the purposes of a VN.