I switched about 2 years ago when I turned on sync. It's just so reliable and fast, it's simple and does its job perfectly. Frequently send tabs between devices and it's instantaneous, bookmarks get synced immediately as well. Also they promise they don't sell our data to advertisers which is a plus, though I can't verify it and they could go rogue in the future idk. Also the fact that the browser is not intrusive at all is a huge plus. No annoying popups "try feature X" "login with your google account now" etc etc.

I do have some issues with it but that's mostly because some people/companies don't properly test their website on firefox. Also had an issue with its performance in the past, but now lately it feels as fast as chrome both on android and pc.