Been using the Fenix 6X Sapphire (Sony GPS chip) and have noticed, it always shows a shorter distance traveled than my other Garmin products.
Last week (In order to test it) I went on a short hike. I brought along my Oregon 650, Fenix 3 Sapphire and the new GPSMAP 66i.
After the hike, the total travel distance was:
Fenix 3 Sapph. 7.59mi
Oregon 650 7.55mi
GPSMAP 66i 7.57mi
Fenix 6X Sapph 7.46
So far, the Fenix 6X always reports the shortest distance. I hope Garmin becomes aware of it and sends a fix in the near future.