My understanding is that internal capacity will play more of a role in consistancy of loads and help keep ES/SD down and potentially better groups vs case weight. From my reading and experience it depends on the size case and manufacturer, whether weighing cases=uniform internal capacity.
I just did a little test last week with my fired 308 Win Winchester headstamp cases. Weighed cases for H20 capacity and then took the ones that had same internal volume and set them aside. Then after all was done went back and weighed those cases and found them to vay by as much as 3 grains in case weight for the same internal volume. So that shows me that I can not rely on case weight in this situation to give me uniformity.
But my interanl H20 capacity for all the cases I weighed did not vary more than 1.5gr anyways. So appear very uniform without having to weight sort