It seems to me that the Fitbit activity minutes is better than intensity minutes on Garmin. On Fitbit it appears to me the activity minutes are calculated based on your heart rate zones regardless if you record an activity. On Garmin they are only calculated when you record an activity and it is easy to cheat. If I want to extend my minutes all I have to do is wait 10 minutes after I have say done a cycle before ending the activity. Garmin will still count that as your heart rate slows. I wish it just monitored my heart rate all day and give me a score based on that.