I've tried many and settled on helmet mount because it allows me to easily sweep my field of view as needed. Yes it gets bumped out of place when stowing the helmet, but it pushes back easily enough. I used glasses mount for a while; problem is if glasses get foggy or rain covered, removing glasses means no mirror.

I have friends who use the bar-end type for drop bars like this https://www.ebay.com/p/5011034059?iid=380891890845

I tried that but found it had limited field of view. I guess that's why some are convex.