Fenix 5's weird calorie count

I've just upgraded to Fenix 5 from Fenix 3 and noticed an extremely weird calorie count, at least with Strength activity I got to try it with. Where for an hour long workout with 146 average HR Fenix 3 had 544 calories, which seemed about right, Fenix 5 counts 727 calories for the same workout which is just too much. Anyone with the same experience? Which of the watch numbers closer to reality?