P99guy, to help with some of your question...
Pyrodex was developed to circumvent onerous HazMat shipping regulations with respect to low-order explosives like black powder, and is treated like smokeless powder for shipping, insurance, and zoning purposes. Ask folks who stock real black powder what kind of hoops they have to jump through, and you'll understand why Pyrodex was considered a godsend. Pyrodex is great for the muzzleloading shooter if your local stores cannot stock the real stuff because of insurance or fire department rules. Otherwise, there's no great benefit.
Pyrodex is purposely formulated to be harder to ignite than real black powder (600 degrees F, with gas temps up towards 4,000 degrees F - which is why you don't see it being used in flintlock priming pans), which makes folks like UPS a lot happier when it comes to shipping and handling. In other words, it's better than nothing, and you'll see it at a lot more retail establishments than Holy Black.
Safe as it is, Pyrodex is considerably more corrosive than even black powder. The corrosivity and ignition properties of Pyrodex drove the industry to come out with other BP substitutes to include the ascorbic acid (Vitamin C) based Pinnacle, Black Canyon, Black Mag, American Pioneer, Clear Shot (fructose), and now the gluconic acid (glucose) based Triple Se7en. All are at least somewhat corrosive, regardless of marketing spiels, and it would behoove the muzzleloading shooter to properly clean their firearms after using any of the above.
Myself, I travel to a store that carries Holy Black, and stock up a case at a time. I like the consistency of black powder, as well as the smell when fired with a proper organic bullet lube. Cleanup to me is actually easier than Pyrodex, and since I can still get real BP, I'll stay with it. It'll keep well, too. I've shot some of my old DuPont BP, and it worked just fine.