The absolute best group I ever shot by a long shot was just under an inch. It was a five shot group with four shot's into .111" at 100 yds. The case was winchester. I don't shoot compatation so I think that I really don't have a rifle that the case will make that big a difference on. I know guy's chase all kinds of gods thinking they are making a better load but 99% of us have neither the skill's nor the equipment to make little things like that matter. If your a hunter the .125" extra, if you get that much, won't mean a whole lot.
I have used a lot of different cases. WW, Rem Fed, Norma, PMC and probably a few others. The best case is the case you have on hand.