While Edge has good and bad points to consider, I stick with it (at least on most of my Win10 PCs), rather than bring in another company's browser.
There are a lot of Win10 boxes out there, and Edge is available by default - so if you can get around in Edge, you can work on any Win10 device (even if someone has Firefox or Chrome setup on theirs).
Also, if I have a non-MS browser, those are more updates to deal with.
I try to limit extensions for the same reason: trying to keep it simple®.
Then there's data collection. How many different companies do you want back-channel chatting with your PC? (BTW, I like Shutup10, to limit the OS to MS conversations). If I ran a Google OS, I'd probably be Chrome only, for the same reasons.
Rationale would be reinforced if the Mail app was better (very weak and fragile). I use full Office Outlook; but that's a full application, with all the resource use. At least Office is MS, so don't have to add a vendor for those things.
A few of the things I don't like about Edge:
- New tab defaulting to MSN "News" page (very slanted to MS's political leanings); but that's easy to switch to frequently used sits display.
- No Silverlight.
- May be Edge causing intermittent "... site can't be reached..." issues for sites I've just accessed.
- Good security/privacy extensions I like in Firefox aren't available.
As usual, it's a matter of compromises, and which ones you feel are easier to live with.