From TFA:
Pocket is a helpful program that many people I know use to keep "read-it-later" web content easily at hand.
Pocket is something I never used and had disabled in my "user.js" file -- and it seems many people apparently did the same. I also have a *bunch* of other things disabled; maybe that helps with performance and stability? In fact, first thing I do when a new version is released is see what new "features" I have to disable. Not a ringing endorsement of Mozilla's development efforts/direction, but at least I (still) have the option of disabling many (most?) things, unlike in Chrome/Edge.
Can't speak to any speed difference between Firefox and Chrome as I don't use Chrome (or Edge), but haven't personally noticed any performance issues. I'll note that I don't keep many tabs open and close the browser when I'm not using it; your use-case and mileage may vary ... The add-ons/extensions I use, like uBO, seem to be better supported in Firefox and browsing w/o then, and especially uBO, seems unthinkable.
I rarely have an issue loading the sites I visit, but the few times it was either a HW acceleration issue, which I could disable, and was corrected based on a Bugzilla report I filed and helped work through; or because I needed to re-enable something in Firefox that a site started using, like Web Assembly -- notably, my bank and USPS.com. Personally, I'd like to be able to whitelist Wasm usage rather than it be just off/on for everyone.
Not sure about all the privacy whinging, but guessing anything in Firefox is better than in Chrome/Edge.