I'm with Joeman on this one.
Not claiming to be an expert pipe smoker at all but I have amassed a cellar of right around 100 pipes. The vast majority of these are estates with a dozen or so cobs and a dozen or so new briars.
At any given time I have around 50 to 60 in rotation. I have noticed that regardless of the tobacco or the method some of my briars smoke hotter than others.
I have simply chalked this up to the fact that no two briars can be exactly the same, being as they are all made from different root balls that have themselves been harvested from different heath trees growing in different climates and terrain.
But, what do I know. ;-)
Just my $0.02
YMMV