On my corporate laptop, I only have Edge and Chrome installed, and I run Edge by choice. I like the horizontal (I meant vertical!) tabs. At home it's Firefox. I guess I mostly just don't want to use Chrome :D
My work PC runs Firefox and Edge. Firefox is my main browser locked down with privacy protections. Edge is left as the default so that corporate stuff doesn't break when I don't need protection from the outside world.
Tree style tabs are good. Great, even. But their UX implementation as a sidebar add-on isn't ideal IMO. Where edge gets it right is the side-tab bar can be automatically collapsed and extended on hover. I don't recall if you can do this with TST - its been a while since I've used it. But the fact that edge's implementation is native and not an add-on, makes it feel far more integrated and less clunky.