Ultimately, the best comparison right now is the Fitbit Ionic. It too offers both fitness tracking and smartwatch features, and works with Android and iOS devices. Not surprisingly, the Ionic offers a deeper focus on fitness and more accurate results.
Slim, swim-friendly design; Works with standard watch bands; Good battery life; Solid third-party app selection; Can play offline Spotify playlists
Requires multiple phone apps; Mixed fitness tracking performance in testing