There are several reasons it would matter. IF, and this is a stretch, you bore/throats are huge and the bullets are too hard. A bullet that is too small and too hard will lead as easily as a bullet that is too soft that is pushed too hard.
So, since ALL firearms are individuals and blanket statements seldom fit, you need to slug your throats and bore to find out what size you need.
Here is what I have learned in the last few years I have cast my own bullets. And, this works in everyone of MY firearms. Bigger is better and matters more than hardness. I have pushed the same size bullets, at different hardnesses at the exact same velocity with the exact same results.
Bigger for me.