After reading 12 pages of back and forth discussion, here is my biased take on Apple vs Garmin discussion.
1. Battery life on Garmin lasts more than AW. But for those who can charge before sleep and during shower, battery life management is a matter of routine for AW users. Marathons or 50miler runs on AW S10 should be more than ok.
My personal experience, for my AW S10 GPS, I also use it for sleep tracking, so brush before bed is when it gets charged for 10-15 minutes and I am good to go for the night. Brush and shower in the morning gets the top up needed. Rinse and repeat, don't have to worry about battery life.
2. Heart rate sensors on AW performs better than Garmin's, AWU Dual GPS also seems to perform better than Garmin tracking, but they are so close, should not be an issue. Wrist HRs has issues with accuracy depending on fit that changes from day to day.
3. Garmin has far more detailed native health metrics data, but with unvalidated/uncorrelated accuracy. AW has apps to supplement what Apple is missing, and many of the apps are single developer apps that have excellent health metrics data, that tells me how having health metrics is not a resource intensive feature that Garmin markets so heavily to consumers.
4. Garmin has very specific tools/feature for a particular sport. AW can supplement this with apps, but might not have all the features that are in native Garmin watch.
5. Garmin watches are bigger, thicker and heavier than AW, it is a consideration when sleep tracking, some sports or even tight fitting long sleeve clothes.
6. Software on Garmin is rudimentary compared to AW. Seen in screen animation, maps, voice assistance, LTE connectivity, feature integration etc.
7. Smartwatch features on Garmin is lacking and is not natively integrated with the phone, so lot of more issues and steps to deal with to make it work well.
Feel free to poke holes at this.
I recently upgraded from AW S7 to S10 and also bought a Forerunner 265, but 265 will go back, and I cannot deal with two watches. S10 does most things that I need it to do well (with WOD & health metrics app), but other things not so well. It's a compromise, one that works for me.