Mozilla is one of the few tech companies that care about the well-being of its users. In my opinion that is very special.
By developer, do you mean web developer?
I tried to use Chrome dev tools, and they were incredibly easy to pick up; however whenever I try to use Firefox dev tools, they feel embarrassingly awkward. Perhaps it's just the familiarity with the tools (and if so, I am very curious to hear whether you prefer Firefox dev tools over Chrome's), but have a nagging feeling that it's just an inferior developer tool.
It was delightful when auditing the experiences from a potential new client in Firefox Dev Tools the other day, and realizing that I could see, inline to the target DOM element, JS events tied to them while looking through the source. Saved me a good amount of time.
When I'm looking for pure-play performance auditing, Lighthouse integrated into Chrome's Dev Tools are an obvious win.
So yeah, each have their strengths and weaknesses.
Just tried that, and wow, that's really cool!