Brass comparisons
Virgin brass, all of the same lot, is the most consistent. As you noted, for a hard-to-find caliber, it may be the only way to go. Norma or Lapua are the 2 brands that serious rifle accuracy buffs swear by. Starline brass for pistoleros.
Next most consistent is once-fired brass, all your own gun, all the same ammo manufacturer and type of ammo (don't put the high-powered hunting round brass in with the target load brass). You have to separate brass from each of your guns and use it in just that gun. Of course the virgin brass is once-fired after a single loading, so segregate it into lots, by intended use, or intensity of load, and keep the lots separate.
I always figured that if I scrounged it from the range, it was once-fired, because reloaders always collect their brass. So if I sorted it by manufacturer and threw out any dubious-looking cases, it was OK for general purposes. Never had a brass failure nor a gun malfunction while using such. Buying "once-fired brass" seems to me like an expensive way to accomplish the same thing.
You may find that your particular weapon has a preference for a particular manufacturer's brass. OK, if Betsy feeds more reliably or is more accurate with Win, or Rem, or Lapua, or whatever, I'll cater to her.