IMO, accuracy has less to do with the head stamp and more to do with picking the right reamer, picking a good barrel maker, picking the right gunsmith to put the package together and making good ammo for the package.
Assuming all those things are done equally well, could you see some cartridges simply working a little better than others?
Maybe....for instance if you had the same caliber as well as the same bore to case capacity ratio in two different cartridges, a very good trigger puller might be able to discern a difference. I think it would take many barrels however, to come to any sort of conclusion.
Once bore to case capacity ratio grow further apart, conclusions about cartridge accuracy would be easier to come by.
