Calculation of calories wrong ?

Hi,
I own both Garmin 235 and S60.
I have different statistics between watches on a normal day with a 4h golf game.
S60 : 11713 steps 2371 Kcal 235 : 11731 steps 2968 Kcal
On all golf parties there is a big difference in the calculation of calories!
The 235 still has a lot more calories burned.
What's wrong ?