Bromite's adblocking is nowhere near as effective as Firefox + uBlock. That being said, I'm using Bromite as my primary browser on Android too because it's much faster and snappier to use and has tab groups. Perhaps I'll use Firefox Android as my primary browser some day.
After that whole search engine scandal with Kiwi Browser, a lot of people don't trust it anymore. I believe it also majorly lagged behind Chromium versions.
It got updated to newest Chromium version recently, the build process seems to be semi-automated now too.
Isn't it open source too?
Unfortunately it's a bit buggy on some of my devices.
Newest FF beta got unexplained speed bost and tablet UI, it's approaching irreplaceablity steadily for me, There's IceRaven FF fork which has enabled even more addons.