Bis
Frankly the big advantage of cast is the price! I am casting my own, and that's a separate hobby which you clearly have no time to do. Leading isn't a problem unless the alloy is overly hard or you are trying to push it to fast or the lube is inadequate. Yeah, I know, adding at least three more variables to the mix when you're just starting isn't fair.
BTW, the best load for the 45-70, IMHO, is a case full of Goex FFG, compressed to fit the bullet in, a 500 gr. cast with BP lube finger seated (don't resize the cases, just pop out the primer) and just enough crimp on to hold the bullet in. I've actually had the bullet easily spin in the case, just not fall out, and gotten excellent accuracy out of an original Trapdoor Springfield.
Wayne the Shrink
There is no 'right' that requires me to work for you or you to work for me!