"Triple Seven is a high energy product designed to provide the muzzleloading hunter with higher velocities when used in the same VOLUME as blackpowder. To duplicate a blackpowder load velocity using Triple Seven, you must decrease the powder charge by 15%" If a powder delivers more velocity for the same volume, it has to be producing more pressure. Because science.
ns.hodgdon.com/loading.html
Other than the ability to get it at Cabela's, or wherever, there is ZERO benefit to the substitutes. Rodwah's friend's steel plates in his mother's basement provides ZERO useful evidence. BP AND its substitutes are corrosive. Period.
Old Eynsford and Swiss, as mentioned above, deliver at least as good and likely better performance than any of the substitutes. Granularity, in these brands at least, offers a much better and more consistent indication of burn rate than the subs. If you are loading limited amounts of pistol caliber cartridges, T7 is not horrible, provided you use copious amounts of good lube. If you are going to use percussion pistols, and BP pistol and rifle cartridges, suck up the HAZMAT fees and get the real Holy Black. In any event, welcome to the dark side !