I haven't seen speed benchmarks or anything like that, but out of the six browsers on my computer (Chrome, Vivaldi, Waterfox, Firefox, Tor, IE) I'd be using Waterfox if I wasn't so Google-dependent. It's fast, with a good UI, and somewhat less clunky than Firefox. Plus it's less likely than Chrome to be spying on me.
I switched to Opera to escape some of Google's tentacles, and that was a smooth transition. If you want a compromise, it's worth a shot.
I then went the whole hog to Firefox.
uBlock Origin, Self Destructing Cookies, and a VPN (PrivateInternetAccess) and I figure I'm getting as good as I can.
The lack of Flash is a non-issue nowadays for me, especially now the BBC are trialing HTML5.
(Although I generally use get_iplayer anyway.)
My primary issue with Firefox is it seems to be really poorly optimised for multicore CPUs. That's entirely anecdotal, but Opera runs just fine on a low clockspeed quadcore system whereas FF is unusable for me.
On my main machine, I get one core with moderate to high usage, and next to nothing on the other cores. Even if it's maxing out one core and lagging.
