Vivaldi was faster, but has a lot odd bugs, it's not OSS, and has no real public bug tracker.
After some recent UI lockups, I decided to try FF57 again. Most of the extensions I use have been ported, but after just a day or two, I started to hit real performance issues again. I'm not ready to give up on FF yet, but I do feel like many of the performance improvements might have been overrated.