Well i assumed the topic was accuracy, and how a case can affect that.
Obviously it does, otherwise benchresters wouldn't spend time separating them, and using the same few over and over.
For most of us, using all the same brass makes sence, and i guess everything matters when you measure group size with calipers.
But ive been to quite a few benchrest matches where some of the shooters load at the match, and watched as the powder goes from the powder measure directly into the case without weighing. Granted, the powder measures weren't part of a $200 reloading kit.
But it does raise the issue of what is and is not, high on the list of priorities as for accuracy.