For me, Firefox doesn't feel as smooth as Chromium, in performance and scrolling. There are also some bugs that occur to me occasionally, but it's not consistent. One bug could occur then I'd never see it again.
A lot of my gripes with Firefox can be fixed with lepton and betterfox, love those two, can't use Firefox without them :)
Can't forget uBlock, too.
For real. I love Firefox but the mobile app is just not good. I have to use Chromium instead of Firefox on my phone because of how choppy and buggy it is 🥲