Man once told me "Accuracy is expensive. So.... How accurate do you wanna be?"
There are EXTREME accuracy cartridges (with the right rifle and right shooter) and there are accurate rounds that began as hunting catridges. Obviously, the 6mm BR, the 6PPC, etc, began as target rounds. To really get the most of these, I believe you will be handloading your ammo.
On the other hand, the 6.5 Mauser is (IMHO) one of the most accurate HUNTING rounds developed, and it has drifted over into the target shooter realm. Same for the .308, etc. But the REAL big boys at 600 yards are not using 30 cals.
Benefits can be argued back and forth over at least a case of beer- how a bullet reacts to wind, the ballistic co-efficent of a given bullet, recoil, availability of barrels and brass, etc. I realize I have not given you an answer, but that is why they have all those flavors in the freezer in the ice cream section.
You may want to read this- World Record Sub-Inch 600-Yard 6BR