Hi,
I’m not sure I understood the question properly, but just in case: ART originates from rawtherapee, but is now an independent project. Of course many things look (and are) similar, but there is no explicit goal of keeping them in sync. They just evolve independently.
In case of doubt about which one to use, with all else being equal, rawtherapee is significantly more popular, so I would go for that.
HTH