I happen to really like the UI of Chrome over Firefox. To me the add bookmark dialog is very clunky in Firefox. Also, I prefer in the in-tab bookmark manager of Chrome over the 'Library' Window Firefox opens.

Also as far as making extensions go I like how in chrome you can use dev-tools-protocol within extensions as you can you cool things like intercept the body of a response with it.

That being said I'm really wanting a better browser but for me Firefox is not it.