Will it actually be worn? This is the single biggest factor. A device left in a drawer helps nobody, so involve the person in choosing between the wrist and the neck rather than deciding for them.
Charging routine. Both devices need regular charging (the Go watch lasts approximately 3–5 days, depending on usage and settings). Building it into an existing routine works better than relying on memory alone.
Who should be called first? Think about which family members, neighbours or key holders should be on the contact list, and in what order.
Where will it be used? If the person is out and about regularly, mobile GPS matters. If they mostly stay at home, it still matters in the garden and on the doorstep.
Tone of the conversation. Framing an alarm as something that protects independence, rather than a sign of decline, tends to land far better — because that is genuinely what it does.