Mostly this, performance is atrocious on a lot of sites I use.

I also dislike its history management, download management, auto-complete, search in address bar functionality, pocket integration, and much more. I'm sure if I were forced to spend more time with it I could possibly find configurations to customize all those things in a way I like, but even using it for a few days the easily findable settings weren't flexible enough.

I realize your comment says you’ve already switched back, but should you ever try Firefox again most of these can be tweaked directly from about:config

I know, but not enough to my preferences at least from as far as I dug into those settings.

To me Chrome has poorer performance, especially when switching between tabs. I've seen Chrome take minutes to "load" a tab.

Yeah, there's an issue on Mac's with scaled resolutions. Not a problem on other platforms, but not sure why it's so sticky on the Mac.

Firefox has awful performance on nearly any web page for me (2014 Mac). Even its own settings page alone puts a core at 100%. I can get past bad font rendering and giving up pinch-to-zoom and not reading PDFs in the browser, but I can't give Firefox half my battery life. I'll use it on my work PC but it's still a huge waste of electricity.

Huh? I read all my PDFs in firefox.

Both Chrome and Firefox are noticeably heavier than Safari on macOS. The most obvious sign of that is battery usage.

Here’s a tip for saving battery on MacOS:

https://news.ycombinator.com/item?id=18048844