The key AW functionality that people seem to call out is step tracking and notifications. They say third party applications are useless due to their slowness to load. Many fitbits cover this at a fraction of the cost, and with better battery life. But Garmin wearables sold me. They add 5ATM water proofing to what fitbits have, plus you can spend a little more and get a device with GPS and 3rd party apps and watch faces.
Example: Vivosmart $129 (no GPS, find my phone, time, notifications, step tracking, touch screen)
Example: Vivosmart HR $149 (better, OLED display and wrist heart rate monitoring)
Example: Forerunner 230 $250 (2 week+ battery life, GPS, step tracking, 3rd party apps and faces, find my phone, color reflective always on display, but button-based)
If you want wrist HR or touch screens on forerunner models, Garmins become less cost competitive; but to me, the third killer feature, beside step counting and notifications, is GPS.