Chrome copied it and at first IMO it wasn't nearly as good inside Chrome as in FF. But that did eventually change and for some years now I (sadly) agree I also prefer Chrome's.
Back in the days when Mozilla put a focus on the needs of power-users and developers...
It's hard to pin down a single point where they dropped that ideal, but it's definitely long gone now.
Dedicated work on Chrome DevTools started only in 2009 and before version 3 or 4 Chrome had only had Elements panel inherited from Web Inspector, Console and gdb-style command line debugger (perhaps basic Network don't remember). It was catching up with Firebug quickly though because web developer tools was stated as a priority for the project.
There are some differences with some of the more advanced dev tools.
I like both