I can tell you why I bought the MS Band: wanted to track my sleep pattern; I wanted to keep a track record of my workouts; I wanted to keep a track record of my running. Why is it awesome: GPS, UV Monitor, optical heart rate sensor; 3-axis accelerometer; skin temperature sensor; microphone; Bluetooth; touch enabled color display; etc.

Convincing reason to buy the MS Band over the Apple Watch: probably the number one reason for me is that it works with my Phone: Lumia 925. Other reasons: cost and availability.