Why even have the entry level Charge? For 20 bucks more I get (allegedly) accurate Wrist based Heart Rate Monitoring, so why would I not spring for the Charge HR over the Charge?
The top end model is a whole $100 more expensive and going into Moto 360 pricing - too expensive IMO.
Better structure:
Charge $99
Charge HR $149
Surge $199
The fact that all of these get 5 days or more of battery life is the key for me. I do not want another thing in my schedule that I need to top up daily - no way.