I`m not sure but I think there is 2 choices Winchester and Remington, af far as the best between these go with Winchester, it is harder.

ho make the best brass to stw hardest and softest

Winchester has been the best for me out of the other 2. I started with-8mm mag necked down and Rem-7stw. With the loads I use it does not stretch as bad and the primer pockets hold up better.

My experiences lead me to believe that this seems to vary more by lot than by manufacturer.My longest lasting brass seems to be 8mmbrass necked down to 7mm.