I use a bluetooth wahoo tickr with my apple watch 3
I'm really enjoying using the apple watch for running and swimming, I'm sticking with garmin for the bike.
The strava app is perfectly fine for running if you want to track the basics, but if you unnecessarily ;) worry about ground contact time or other crazy metrics, then I'd steer clear of apple for now. Same with swimming, its good, but you don't get the same amount data as a garmin would give you
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