I always hated SAI's user interface, it's butt ugly to me( hopefully I won't burn on stake for saying this). Never left a good impression even with great brush engine.
Also it felt unfinished, lacking tools, and if there are no substantial upgrades and steady development, I am afraid it will stay in the "cult" zone.Maybe I didn't understood what the hype was all about.
Clip Studio Paint is ,IMHO, eclectic piece of code, love the line tools, rulers, UI, blending, 3d, everything, and now with translation workflow it will become my main workhorse,
hopefully replacing IllustStudio which I cherish and praise, along with mammoth Photoshop64bit.