I was going to add a stipulation about the about:settings type stuff being different and what not, but chose not to originally. My thinking was how often are you in settings that it's a problem? I'm not a browser power user, so I only go in to the settings usually after reading something here. I set it, and forget it. Maybe 30 seconds?

As far as dev stuff, I'm really only familiar with Firefox after Firebug was rolled into the browser so that it is similar to Chrome with a Cmd-Option-i key press. I hear people stating that the dev tools are still very different. All I really ever use it for is seeing how the DOM is changing in the inspector, looking for output in the console, and see what files are doing (404,200,500, params/response, and CSS values type of stuff. Both browsers do what I need in a way that I can't tell the difference.

It's almost entirely the more in-depth stuff. For example, differences I find annoying include seeing raw ajax values, re-runnning those queries, and how Chrome can't select individual log levels to view in the console.

On top of that, various parts of Firebug's console UI was better than either one's current console, mainly in how it displayed data.

I felt like this as well when I was still using Chrome for everything (I switched when Firefox launched Quantum). For me it simply turned out that after getting used to Firefox (again) I had no problems at all with the UI. Chrome felt better before the switch because I was used to it.