Chrome dev tools are equal as powerful, and regarding the other comment about speed. I have tried the new firefox and chrome still flows better. The reasons posted here are not sufficient, sounds like the firefox users are just loyal.
Chrome's features don't constitute a superset of Firefox features and vice versa. Examples for features exclusive to Firefox:
1) Tab groups 2) Awesomebar (which works very differently than the Omnibar) 3) History sync 4) Load tabs on demand 5) Bookmark tags 6) Livemarks 7) Better resource usage (especially memory)
And I could easily add several more, both native as well as the ones added by extensions. You may not care about some or all of these features because they don't fit into your browser usage pattern, but others do. Speed is also important to me and I'm glad that Firefox gets improved with each new version currently but it's not the deciding criteria as long as it doesn't inhibit me from using the browser as I wish.
Obviously FF is far from the perfect browser, I hate that it doesn't use native ui elements on web pages(e.g., the `select` html element) and I think it's a bit more resource-hungry than Chrome.
Depends on what you measure and your usage patterns. Firefox runs circles around Chrome with regards to memory usage and features like "load tabs on demand" can further lower the general resource usage drastically.
The lack of native UI styling of 'select' elements is a disgrace though, especially on Mac. Firefox is the last browser to exhibit this and there are no sign that this will changed in the near future. :-(