different stoves, same pellets, different heat output

[davevassar]

I have an Enviro Empress insert, and my father has (I think) a whitfield insert. We have tried different brands of pellets in both stoves, and the difference in heat output baffles me. For example:

Green Supreme - throws ok heat out of my stove, and great heat out of his.
Barefoots - The best heat I've gotten out of my stove. The worst out of his stove.
Fireside Ultras - good heat from mine, not so much out of his.

Why is this?

 

[rayttt]

biggest difference probably would be air flow into unit..

 

[69800]

I once ran an old whitfield legend out side with another stove of a little newer vintage (cant remember brand) at the same time.. the whitfield on medium (flame about 6 inches high) almost burned my hand 6 inches from the room air blower with almost not heat coming out the exhaust. The other stove on high with the same flame height and perfect damper adjusting was about 50 degrees less temp out the front and the exhaust was very hot.. Both stove were rated at 18000 btu.
I think there is a big difference on the efficiency for brand to brand and model to model.
mark

PS air flow out the front felt pretty close to the same