Calories difference between fit bit and Garmin

Expect the step count to be lower than on the Fitbit as well. 
I think the numbers from Garmin are more realistic. Fitbit knows that their customers like higher numbers.

You can double check the heart rate by counting manually.

That in fact was why I went from fitbit to Garmin years ago,  Fitbit was very generous when it came to steps, and I did side by side tests of fitbit vs a few other trackers, and fitbit was always higher than the other trackers (and not just a few steps).  At the time no one complained as it was easier to make your step goal with fitbit.

The step difference isn’t too bad for example fit bit had me at 22,000 and Garmin had me at 19,680 which I can imagine was arm movements. 

So what would you suggest as far as considering Garmin to be more accurate when I am very fit , 42 , 80kg , average 15,000- 20,000 steps , use sauna , HIT running , weight training and long walks yet it takes me around 90 mins of any of the above just to hit a use of 2500 calories a day which I assumed was average !? 

I was thinking if this is correct it’s due to my high Vo2 max score and lower heart rate due to fitness levels !? 

It’s all good news if true apart from I still have to be disciplined calorie wise no matter the amount of exercise I do …….

So what are your resting calories? I am 78 kg and 50 years old, and my Garmin watch says I have 2069 resting calories. I takes me less than 90 minutes to add enough active calories to reach 2500. 
My resting heart rate is 43, and VO2Max is 53.

So give or take we have the same stats so what type of activity gets you to 2500 and 3000 calories? 

It just seems when I am generally moving or extremely active it doesn’t increase much more where as the fit bit would have me at a extra 500-1000 calories or so 

Examples:
Running a 10K in 45 minutes earned me 668 calories. 
Running a 10K in 55 minutes earned me 733 calories.
Cycling 12km in 35 minutes at very easy intensity was 250 calories.

If you want to get lots of indicated calories, try the "Cardio" activity. It typically overrates the heart rate and work done.

I get a short report that includes average heart rate after the activities.

Yesterday I did 25 mins HIT treadmill , 45 mins intense weight training , 30 mins sauna and total of around 15,000 steps and total calories burnt was only 2775 does that seem right ? 

Yesterday I did 25 mins HIT treadmill , 45 mins intense weight training , 30 mins sauna and total of around 15,000 steps and total calories burnt was only 2775 does that seem right ?