I have for the most part gotten away from .452 bullets in favor of .458 bullets. The main reason is that the .458 bullets were designed for the speeds we are pushing them with the muzzleloaders. .452 and smaller..MOST of those bullets are designed for handgun speeds in the 700-1400 FPS range.
I have also found better accuracy for the most part with the .458 when you find the correct sabot fit for your MZ.