Difference between systems?

I'm about to switch over from Brewtarget to Beer Smith, but when I compare these systems, I get a little curious. Recipes in Brewtarget has more grain than in Beer Smith for the same ABV and I do not know if thats wrong or if it should be so but I'm a little curious about how it works.

It sometimes feels like there is a bit of fortune figures in Beer Smith or is it just me who has the wrong settings.

Anyone who feels that it wants to give an explanation? I enclose recipes from BT & BS systems if anyone wants to check

Variation between programs is a common occurrence. If they all had a unified voice of predictions, then what would be the point of switching?

Does Brewtarget work off Brewhouse or Mash Efficiency?

Your post hints at a possible confusion about the two. If you plugged in your Brewtarget mash efficiency into BeerSmith, you're not getting an accurate prediction. But, it would act as you described.

Brewhouse Efficiency (BHE) is used to describe your whole system, not just the mash extraction (ME). BHE is measuring the fermenter, ME is measuring the kettle.

When you input 80% BHE, you're saying that of all the total available sugars, 80% of them will end up in the fermenter. So, adding loss between the kettle and the fermenter won't dilute the gravity because you've stated that 80% of the total potential sugar will still get to the fermenter. Therefore, the ONLY place that the sugar can come from is increased mash efficiency; which BeerSmith calculates automatically.

Put into practice on 5 gallons, if your system can get 80% ME, and you have 0.5 gallons of trub loss after the boil, your BHE is about 10% less than the ME because the trub loss represents the sugar percentage that didn't make it to the fermenter. So, your BHE would be around 70%. In turn, this would increase the amount of grain needed to get the same gravity.