Since several brands are owned by Vista Outdoors, I just buy the specific cartridge I want at the time (on sale). Only difference is for my favorite calibers - .22 Hornet, .45-70, .32 Win Special, and 10 gauge. My son worked for Vista (RCBS). He told me that the less-popular calibers are produced only on rare occasions, so it's best to just bite the bullet and buy when available. Ammo companies produce what is in greatest demand because anything sitting in distributers'' warehouses turn no profit.
Now that we are once more in a "Happy Time" of abundant, relatively cheap ammo, shooters can be picky, look for bargains, and have more fun shooting.