I actually really like Edge despite being a Firefox fanboy from it's conception.
I found that over the years the growing number of issues I was having with Firefox led me to give Edge a chance, and after a few months of tweaking I ended up really liking it.
The slow speed of Edge's toolbar autohide in fullscreen mode is practically the only negative for me now.
Firefox, for example, shows and hides it instantly, and it doesn't cover any of the content when it does. It moves the window down so that it doesn't obscure anything.
But Edge is painfully slow to unhide it, and also won't hide it again unless you stop moving the mouse for a second or two, or click the window or address bar. It also obscures the top of whatever site you're on. It really slows you down when you constantly have to stop and wait for it.
Using an OLED it's not good to have a static toolbar that's always there when browsing, and can cause burn in.
A big plus is that in fullscreen the little white line at the bottom of window that they introduced about a year ago goes away. (Think it's only visible in normal view if you've disabled the rounded borders)
Not optimistic that this post will lead to any action, but maybe the their competitive side might be sparked by showing the difference in the tool bar show/hide speed between the two browsers.