Black Powder is already classed as an Explosive. That's why a lot of gun stores don't carry it.
For a Dealer to sell Black Powder, he must have a Federal license for explosives.
His Insurance rates also go up because he has an Explosive in his building.
Pyrodex, T7 and the rest of the substitutes are classified as Combustables like smokeless powder so the Dealer doesn't have to screw around with extra licenses.
I've shot many pounds of Pyrodex P, Pyrodex RS, and one pound of Select.
I have not shot the other New powders so I can't give a personal opnion about them.
The Pyrodex does not foul the bore as badly as real Black Powder does. In fact, I can easily shoot all day without wiping or loading problems.
Some say it leaves harsher chemicals in the bore so giving your gun a through cleaning is even more important than if you were using real BP.
IMO the Pyrodex Select is a total rip off. It costs more and was not as consistant in accuracy as the RS which works very well in my precussion guns.
As for Pyrodex being 15% more powerful than Black Powder this is true IF you are talking about power Per Weight.
This is Not True if you are talking about Power per Volume.
In other words, if your measuring your load with a hand held powder measure or dipper, like most all Muzzleloaders do, do not reduce the load from the Black Powder load.
If you are measuring the loads real Weight on your weight scales, then reduce the load.
From what I've read on this Forum, T7 IS more powerful per weight OR volume so you should reduce the load about 15% from the powder load you've been using.
This higher power thing is also true if your fortunate enough to be able to shoot Swiss Black Powder.
It is just better stuff and it requires reduced loads of it to hit the same place on a target. It also burns cleaner than Regular Black Powder.
edit) Another thought: The ignition temperature of Pyrodex is several hundred degrees higher than Black Powder. That is the reason it works very poorly (if at all) as a propellent in a flintlock. Even with a good flash in the pan and a clear touchhole to the chamber it usually won't fire.
This higher ignition temperature is also why Some caplock rifles have delayed ignition when they use it but they work great with regular Black Powder.
Another thought: Use the LOOSE Pyrodex if you have to use it. The pre made Pellets will not work in a sidelock gun. They are made for use in In-Lines Only.