Timed some tasks in the old and new (Quantum) Firefox that I routinely do tonight, achieving each task the fastest way I can find in both browsers.
1) Saving a bunch of photos of some bugs I wanted to keep from a webpage for reference and putting them in the proper directories.
Old Firefox: Less than a second
New Firefox: Seventeen minutes
2) Organizing Tabs (including closing certain tabs and not others, selective bookmarking without navigating to tab, etc).
Old Firefox: Five minutes for about two dozen tabs
New Firefox: Infinite, as it’s not possible
3) Switch Proxies between VPNs
Old Firefox: Less than a second
New Firefox: Infinite, as it’s not possible
As I was writing this, I realized timing anything else was pointless as most of the things I want to do are simply no longer possible at all in the new Firefox.