there are advantages and disadvantages to each, you'll have to decide which you like best based on yer own testing. my observations are
1. pyrodex fouling does not build up like blackpowder fouling. it still gets all over everything, but it doesnt accumulate and cake like blackpowder fouling does. i have shot guns side-by-side with the two propellants, and the difference is very noticeable to me.
2. blackpowder produces less hangfires and misfires than pyrodex in sidelock muzzleloaders (doesnt seem to make a difference w/ inlines). i can make pyrodex work very reliably in my sidelocks, but it requires some tapping on the breech of the rifle to make sure powder has entered the bolster. blackpowder is pretty much a sure thing for ignition. just pour it in the barrel and blast away
3. corrosiveness: in my experience, pyrodex is actually MORE corrosive than blackpowder, even though it produces a little less fouling. i once had some light speckling on a stainless steel bolt
after just one day of sitting w/ pyrodex fouling
4. accuracy. my results have been inconclusive on whether one is more accurate than the other. pyrodex claims to produce better shot-to-shot consistency because of the lower residue build-up, and that makes sense. but in my actual experience, i have shot some truly outstanding groups w/ blackpowder, while i can't say that i've ever really shot a remarkable group when using pyrodex (have done really well w/ triple 7, though).
5. shelf life . . . ?????? ive read plenty about this, and some folks indicate that pyrodex has a shorter shelf life than blackpowder. mebbe so and mebbe not. i will say that i shot some pyrodex RS last year that has a date of 1994
, and it shot just fine (the seal on the bottle was broken back in 94, too). blackpowder doesnt ever seem to go bad
anyway, i shoot both of 'em. they both work, just have different characteristics. my decision is oftentimes based on which i can get the cheapest . . . .