I want to like Firefox, both as normal user and as web developer, but something about it keeps bugging me. The UI feels sluggish, sites seem to be slightly less performant, and I can't seem to get used to it.
I feel the exact same. I use linux with a tiling window manager and when I change format, Firefox just starts twitching like it's trying to give me an epileptic seizure while chromium browsers do it just fine.
Also, sometime ago I tried to compare Chrome (when I still used it) and Firefox side by side with the same extensions opening the same websites and Firefox always took a bit more ram.