This is totally hyperbolic, but think of it as asking why a F150 uses more gas than a Honda Civic even though they’re going the same speed, and the same distance. They’re built for different things. AW is smartwatch first, while Garmins is a fitness watch first. They wouldn’t be using the same processing power as they have different chips. Also different ram, screen (Garmin Epic is 1.3" 416x416, AW is 1.9" 502x410), background activity, etc.
This is totally hyperbolic, but think of it as asking why a F150 uses more gas than a Honda Civic even though they’re going the same speed, and the same distance. They’re built for different things. AW is smartwatch first, while Garmins is a fitness watch first. They wouldn’t be using the same processing power as they have different chips. Also different ram, screen (Garmin Epic is 1.3" 416x416, AW is 1.9" 502x410), background activity, etc.