i like vivaldi a lot :) mostly because of its UI and extremely easy in-depth customization. in my opinion it is the greatest-looking web browser (if you don’t factor in all the css fiddling you can do in a text editor with firefox, of course. but even then i don’t recall seeing any custom firefox user style that looked better than vivaldi to me).
the reason why i switched away from vivaldi and back to firefox after ~2 years of straight usage was that vivaldi had a weird performance bug for me where if i had too many tabs open for too many days in a row (laptop, no shutdown), it would randomly start freezing and i’d have to restart it. but when it was running on a fresh start, it was amazing. also the more ethical choice of using a non-chromium browser was part of the reason