Firefox is faster than Chrome for me. Theme isn’t an issue for me, but the thing that took me a long time to get where I like it, is getting rid of all the buttons and UI elements and plugin icons that I didn’t want to see all the time to get things streamlined down to where I like them. It did take me a couple months to get everything how I like it, but now when I use chrome, it seems clunky.
Trying to switch tools takes a while to get right and to re-learn. There are some things I don’t like about Firefox still, but more I don’t like about Chrome.