Awaiting a review based on a slightly longer usage, we publish a cycling session recorded with the two Garmin devices in this article. The Fenix 5s used its Gps and cardio sensors while the Edge 820 recorded its data with the help of a soft cardio Premium soft tissue and cadence and speed sensors combined with the Garmin computer cycle.
Differences on lap
Difference for each Km in terms of time detected, in green the Fenix 5s in blue Edge 820.
Same thing but with 5 km step, always in green Fenix 5s and in blue Edge 820.
Red line is heart rate and green Edge 820 speed. In blue speed and orange heart rate of Fenix 5s
In fact there is a difference but it looks really slight. Soon for other data.