I use Firefox exclusively to browse, I use Chromium for local development.
It is true the Firefox's dev tools are a lot better now than they used to be - I use them regularly when I test sites cross browser. But they lack critical features like source editing and stack rewinding, and the tiny visual/layout improvements they've made are not enough to get over that. In Chromium, if I pause a script, I can edit a line code earlier in the function, resume, and Chromium will rewind the stack to that point and replay it forward with my changes.
It is insanely useful, hands down the single tool that I use most often. Stuff like that blows Firefox's dev tools out of the water, because it turns out that I debug Javascript more often than I debug Grid layouts.
A while back I looked into whether or not anyone at Mozilla was working on something comparable, and there was somebody. But then everything went silent and I don't know the status anymore. I've been wondering for multiple years now why this kind of stuff isn't higher priority than new Grid tools or color selectors or whatever.
Firefox's dev tools are way behind Chrome's in basic functionality, even if the user experience is otherwise excellent. You can't even set breakpoints on DOM elements. I would disagree with anyone who claims that they're even remotely comparable tools at this point.