I think the virtue, if any, of the pellets is that in a hunting context and iffy weather they are easy to manipulate and load into a muzzleloader for a follow-up shot.
I have done some 45-70 BP reloading, very basic and with good results (in spite of all the gyrations Ive read about for BPCR loading), a primed case fire-formed to the chamber, as much 2F as fits in under the bullet with just a little squeeze, no card or lube wad, and topped by a 405gr. cast bullet with some TC Bore Butter smeared into the grease grooves. The bullet dia. fits the case mouth a tad snug.
I havent fired a bunch at one sitting, but what I did went where I had it pointed out at 125ish yds. and I had a nice 'lube star' at the muzzle showing that the lube lasted the barrel length.
All in all, certainly good enough for hunting all but a 'herd' hereabouts.