Multiple and fully isolated user profiles - hugely important for the work I do. I know Firefox has containers, but they're not really feature complete compared to Chrome's, and the UI experience leaves a lot to be desired, there's just to many friction points.

edit: forgot to also mention, I'm also aware FF has profiles as well (about:profiles) but the implementation has too many speedbumps. As I mentioned in another post on HN, the profile manager needs to be an upfront and first class UI citizen, something hidden away with a fairly poor UIX.