Almost a decade ago that was true. I use budget Android phones, and Brave was the only ad-blocking browser I could use. Firefox with ad-blocking plugins was slower than Chrome with ads. Brave was chromium based and was by far the most responsive way to browse the web.
Firefox got their act together and now the Android version is great. And the plugins work well. Brave began substituting some site ads for their own ads, if I remember correctly. You'd see fewer ads, but Brave was getting some money to let a few through.
Firefox got their act together and now the Android version is great.
It's fine, but I wouldn't go as far as to call it "great". There are still some bugs that simply don't exist on Chromium-based Android browsers. For example, there are many cases where if I seek a video it will reduce the framerate to something like 0.5-1fps for 10 seconds or so. Not to mention some video codecs being completely absent. Yes, I know there's licensing shenanigans going on, but at the end of the day Firefox can't play some videos that Chromium can.
I will concede that Firefox (on Android) is in some ways superior to other Chromium based browsers because of add-ons. They're very nice, and I've had no problems with them.