There must be something different about my web use, because I keep hearing anecdotally that Firefox has reasonable performance relative to chrome. My experience is now and has always been that they aren't even close. I'm working on a React app at the moment and just confirmed: some basic operations that are buttery-smooth and instantaneous in Chrome have noticeable delay in FF. No extensions installed in either.

Firefox has almost imperceptible jank, but it is there if you squint.

Since forever I have a test that firefox always fails at: on first load, or if you haven't right clicked in a while, the context menu takes a perceptible amount of time to show up fully, and within this very short amount of time, you can visually see the menu options cascade out as the CSS engine finishes laying out and rendering the context menu.

This kind of jank still happens on latest firefox. It's little things like this that make it feel unpolished.

I never observe this behaviour on Chrome.