Firefox
An established foundation with good interests and goals running it (unfortunately it's not quite that clear cut - but the best, closest). The source of free software development. Extensive feature set. Robustness.
I haven't seen the need to use a fork, and like and prefer the idea of using and supporting the one that's investing in the engine development - even if it's largely only through free use. (Using forks does not support them this way.)
When briefly using chrome dev tools I've always preferred and went back to Firefox dev tools for web development.
Sharing my data with an independent org like Mozilla feels much better and safer than with Google. The services are free software and could be replaced if it ever need be. Still, Mozilla is big enough to expect stability across time.
Tech wise there's not much difference between the three big players Firefox, Chrome, and Edge.
If it weren't Firefox I'd feel more comfortable with Edge than Chrome.