What I see is benefits around battery life, form factor (buttons are awesome), and good native support for "compound metrics" like Endurance Score, Hill Score, Training Status, etc.
But when it comes to actual stats and metrics, Apple Watch feels superior in most ways. Garmin sleep tracking anecdotally feels much less accurate. It baffles me that it only shows pace to the nearest 5 seconds during a workout. It confuses me that it only shows a Vo2max estimate to zero decimal places.
Then, Apple Watch is at least 10x more customizable via third party apps. Want a Whoop-like experience with strain score, recovery score, etc.? Bevel and Athlytic are there. Want a much more in-depth and customizable workout experience? WorkOutdoors puts Garmin to shame here.
What am I missing that makes Garmin so pervasive, while Apple Watch is derided as "not a serious sports watch"?