.308 for long distance shooting and a .204 for 200 yards or less. The only reason why I dont go out futher with a .204 is wind drift. But most of this questions relys on the shooter more than the round. Many good top notch reloaders can custom load rounds that will out perform any factory load . So I'd say 50% shooter. 25% gun 25% ammo. No I take that back 100% Ammo , 100% Shooter and 100% Firearm.
Its like golf you have to have all three to stay in the game.