Strange. I almost exclusively use OSX (El Cap) and haven't had performance issues asides from needing to restart the browser once a month or so. Hopefully they get those problems resolved soon, the browser is super quick when it's working right.
Are you using a "scaled" resolution? If so, there's a bug in redrawing that pegs a core, and kills battery life.
It can be mitigated by setting
gfx.compositor.glcontext.opaque = true
in about:config, but the fix is invasive, and has taken years to get prioritized and worked on. I've seen reports that it should finally be done in FF64 or 65.
I find that I cannot watch a YouTube video on my MacBook in Firefox for more than 10 seconds without the fans coming on at full throttle. This is one of the few reasons that I start up chrome, as strangely I can watch the same video in chrome without performance issues. I haven't had this issue on Firefox on PC
Google Sheets and Google Docs have been horrible on anything than Chrome for a while as well, and I guess they have no incentive to make that situation change. Firefox is dealing with it better than before I think, but I won’t hold my breath for parity to ever come.
Also, on my 2-year old MacBook Pro, the thing heats up pretty bad and the fans go on quite loud. It's terrible. I've actually never run any application on my laptop that performs as bad as Firefox, and that's saying something.
There is a significant (maybe 0.4-0.5 seconds?) lag between the cursor hovering over something and it's hover action (highlight, whatever) taking place.
Running my mouse down the list in about:config feels like I'm drunk.
As a follow-up, I did a complete reinstall of Firefox with a new profile, removed as much cruft as I could (pocket, etc.), upped the content process limit... and I feel like Firefox is much more usable. There's still some lag, but it's more on the order of 0.05 - 0.1 seconds.
Now if I could just get it to be reasonable about search engines...
GP claims that FF performance is terrible, which I cannot endorse (I guess GP might be having an actual issue), but I'll make a different claim: performance is not as good as Chrome (or maybe even Safari), despite all the accolades of FF Quantum, and my myriad attempts to switch to FF. The (at least perceived) inferiority of performance in addition to general UI ugliness makes it a no switch for me.
Sorry, if that was your thought, I’m afraid all design is probably lost on you. Which might be a blessing, since you can use whatever and can’t tell the difference anyway.
