Good post. But reading both articles, Hawks despised Pyrodex but White recommends it! (at least Pyro P)
The more I read Chuck Hawks the more I disbelieve him. I am sure, if you left a ML uncleaned for a long time using either BP or Pyro, or T7, or even BH209 it will ruin a barrel. And the corrosion, I agree, would likely be at a different rate for each propellant. Heck, even if you left a centerfire rifle uncleaned using smokeless powder long enough it would corrode. So is one powder worse than another if proper precautions are taken after use to remove all residue and treat the bore with a preservative oil? From a corrosion standpoint I don't think so.