Similar boat here. I abandoned Firefox back in the day due to the memory and freezing problems, and general lack of responsiveness compared to Chrome. The difference in everyday use was massive here; we went from having a browser that could hardly handle having 3 tabs open while using a gigabyte of memory, to one that worked flawlessly and used a fraction of the resources. Firefox then put in a lot of effort fixing those issues. By this time though, Chrome's built-in DevTools was more robust for my tastes compared to Firebug or the horrific early versions of their built-in replacement. I had a good development setup, all the addons I needed, and a fast browser. I simply had little reason to switch back.

I did spend a brief period swapping back to Firefox for the sake of perceived privacy, but then they started bundling all sorts of third party bloatware and it was just too much. I'm not a superfan of the information I imagine Google collects from my using Chrome, but the browser itself is just too good to give up. Firefox now only gets opened to verify cross-browser functionality of frontend UIs I work on, and on rare occasions when I want to use a proxy in a browser without it being used system-wide.