It has a monopoly on being non-Chromium based

On Android, Firefox is still less secure than Chromium-based alternatives: Mozilla’s engine, GeckoView, has yet to support site isolation or enable isolatedProcess.

From Privacy Guides. Firefox on desktop though!

For me personally, the one and only reason I don’t main Firefox is because it doesn’t work with Chromecast and I use that a LOT. I would switch to FF tomorrow if I could easily and reliably cast with it.

It works almost exactly the same as Chrome.

A little slower, but nothing. Mullvad is pretty good. A mix of Firefox and Tor.

Nothing. I use it all the time.