None plus 0. Except for specialty use like endurance sport battery life nothing I've seen or tried is in the same league. My watch is also my phone for more of my reasoning.
Fitbit Versa, for me. It does everything that I need as a Smart Watch, and is a great fitness tracker. In fact, my wife and two kids use the same one with their iPhones.
Garmin Vivoactive 3 Music. Was more interested in fitness tracking than an amazing smart watch. It's perfect for me and the connect app has pretty advanced fitness metrics compared to the apple one. You know, when it isn't being held ransom by Russian hackers.