Syncing active calories

I use Samsung Gear S with S Health app and also Pacer to sync with MFP. Today I noticed a difference in logs as following:
Gear S /S Health - 10557 steps (app used Gear S watch)
Pacer Steps - 9706 steps (app uses phone's inbuilt pedometer)
As those steps were recorded I also did a walking exersise, which was tracked on both Gear S and Pacer. The results read as following -
Gear S / S Health - Distance - 3km; Calories - 107;
Pacer - Distance - 3km; Calories - 94
The above are not significat discrepancies but then I looked at the shockingly synced totals.
Gear S / S Health reads - 389 calories burnt so far
Pacer - 283 calories burnt so far
So I looked on the Gear S / S Health individal activity breakdown which stated 10557 Steps - 338kcal burnt and the Walking Exersise - 107kcal burnt so if we add those together it gives us 445kcal total. Now having it compared to the total calories burnt 389 on the S Health app i undersatnd that the app syncs steps and waking excersise so that it doesn't double up i.e. the amount of calories burnt is correct. Now what about the Pacer?!?!? And does adding the continuous heartrate monitoring to the steps, time and total distance make such difference in calorie calculations?!?!?
What are your thoughts guys?