Garmin and Apple are playing in different leagues. The tracking data a Garmin watch delivers just isn‘t comparable and Apple Watches are just a toy in comparison.
the real benefits of an AW can be found in the deep integration into the Apple ecosystem. It can unlock your Mac and it has a huge pro with Apple Pay.
But talking about battery life or connectivity, the Apple Watch is just a joke. Have you ever tried to connect the heart rate monitor of the AW to e.g. your bicycle computer (Garmin, Wahoo, whatever ..) - this is not possible just because Apple does not want you to. Third party device manufacturers would have to pay Apple and implement GymKit Hardware (which also uses only BLE to transfer data) to make this possible.
Apple, just works.