I love how much you can pimp out Firefox with custom CSS style sheets. However, the number one reason I use it is to show the internet that not everyone wants to just surrender to Chromium (and Google). If I could donate specifically to Firefox development, I would.
I have Brave as a backup and still use it from time to time. It’s a good browser. Privacy-wise it is probably better than vanilla Firefox but inferior to Librewolf (a security-hardened Firefox fork).