Been a Firefox fan since inception, but the last 1-2 years I have mainly used Brave for two reasons:
1 - I get the privacy things from the get-go rather than having to configure and install add-ons and whatnot.
2 - Firefox does not fix large-resolution displays that well in Linux. On a 4K TV with 200% scaling, fonts and stuff get annoyingly big.
On my Ubuntu desktop, a script on my homepage correctly reports my resolution as 2560x1440 with Brave, but Firefox says it's 1246x1338 for some reason. No scaling set anywhere. Also, when no special fonts are defined with CSS, they are way thicker in Firefox than in Brave.
Firefox on Android is not quite great either. I don't remember exactly why i got disappointed, but I think it had to do with the rendering as well.
Still keep Firefox on my desktop though because I store a bunch of passwords in it.