Are you comparing current Chrome to current Firefox? Relatively recently, compared to the overall trend we're seeing here, Firefox got much faster than it had been: https://blog.mozilla.org/blog/2017/11/14/introducing-firefox...
The discussion above, however, is about how Chrome came to grow so much while Firefox shrank so much, and for that the question is how did Firefox and Chrome compare historically. There was ~10y from Chrome's release until Quantum came out.
(Disclosure: I work for Google, speaking only for myself)
Even opening a select box is slow, if you have several 1000 tabs.
Funny enough, opening a new window (and keeping all the other tabs open) makes it fast again, if you are in that window.
Seems like Firefox has some slow code paths, like notifying every tab about going fullscreen?
Is it possible to have 1000 tabs open in Chrome? When I had like 50, it ate my whole 8GB last time I tried it.
In Firefox I frequently have 1000 tabs with no issues. (almost none, recently I noticed that there is some memory leak and the ram slowly disappears).
This is the reason why I went back to Firefox after using Chrome for like 2 weeks, it is great for 1-10 tabs.
Chrome kills them regularly on it's own, which means they simply crash with out of memory.
For me, Chrome generally handles killed renderers better, e.g. it shows a popup about crashed extensions and just reloads them. Firefox requires me to quickly disable and enable adblock and I lose the build in screenshot extension permanently (except disabling and renabling it with about:config). But for chrome a renderer often just freezes and only a day later there is a popup about it which offers to kill it.
Firefox seems to handle the tabs better overall, but at some point session resume fails with javascript errors in the shell. Chrome seems to handle session restore a bit better.
Also FF was shitty at stability, it didn't have multi process architecture for the longest time and I've had a page crash my entire browser (especially in the flash days) regularly.
And then chrome started pushing excellent dev tools (even in FF nightly I get dev tools hanging on complex sites because of how slow they are)
Chrome was the better browser back then and it won the power users and developers, then it took over the casuals as it was advertised on google and it was recommended as the best by everyone - it took FF too long to catch up and now a lot of sites don't even test compatibility - I've been trying to switch back to FF before this fiasco for a month and it wasn't a smooth experience compatibility wise.
WHo cares? A Ferrari and a Lamborghini in 2020 provide about the same speed experience. What matters is that for the past 10 years Mozilla had the speed of an old Volvo versus the Ferrari that was Chrome/Chromium in comparison. The fact that Mozilla merely caught up in the end is rather a proof that they lost technical leadership a long time ago.
Speed's always been similar for me, Firefox has generally been more reliable (partly due to being able to block so much crap, probably). Chrome used to break with alarming regularity and need a total reinstall. Sometimes there was a site which wasn't compatible with Firefox, and if I needed it I'd open it in a Chrome incognito window.
These days I've switched to Vivaldi for the work stuff (vertical tabs, "hibernate background tabs", tiling!), though I still debug JS in Chrome.
Really the parent commenter is right: Chrome is dominant only because of its huge marketing budget.
P.S. Chrome is also buggy as hell and crashes pages all the time, which Firefox doesn't do.