Just curious but why? I use FF regular on mobile, mostly for the ublock, but I wonder if I'd be better off with Focus.
My reason is mostly the above (and other related security reasons). In particular the ability to clean sessions, cookies etc. just by hitting the trash can next to the URL bar.
Secondary reason is on a small screen usability. The simpler the better. Firefox Focus is simple, minimal settings, and of course quick and easy to reset sessions.