Choose emergency alert buttons when the question fits its direct job: it send a manual request for help when a user presses a wearable or fixed button, relying on reach, deliberate activation, radio or cellular connection, response-center routing, location information, battery, and an agreed emergency plan; gps safety wearables instead share wearer location and movement information through satellite and network services.
The word instead makes this a use-case decision, not a ranking based on added features. A situation favors emergency alert buttons when the required job is to send a manual request for help when a user presses a wearable or fixed button. A situation favors gps safety wearables when the required job is to GPS Safety Wearables.