All my brass comes pre-loaded
In 36 years of loading I have never bought brand-new, unfired cases. I buy commercial ammo when I need to increase my stock of reloadable brass.
I know I am taking pot luck on quality, but the variation inside one lot of brass from the same manufacturer is WAY below my ability to detect in point of impact.
Now, if I was shooting 1,000 yard benchrest competition and wanted to get that last quarter-inch out of my group size, I would invest in not only buying brass from the best manufacturer I could find, but I would do all the other things (flash-hole uniforming, weighing cases, measuring web thickness and smudging with incense, etc.)
I figured it out once. Brass that comes pre-loaded is slightly more expensive than new empty brass (after adjusting for primer, powder and bullet). But the convenience of not having to load is worth that small amount. Besides, it gives me factory ammo to compare my handloads with.