Until most of the Chrome extensions will be transferred to Firefox and until developers will actually start doing extensions for Firefox, it won’t be really helpful. I tried it as well, it might be faster, it might be lighter (I mean memory consumption for instance), but it’s quite useless without extensions that I have at Chrome.

And yes, like people commented before, most of those things that you described, at least for DevTools part, are already implemented in Chrome. So I don’t see any reason to switch to Firefox now.