In off the shelf factory rifles I dont think you will see much difference accuracy wise. In a accuracy built custom rifle I think the 222 will win by a little bit. I have had 222s in bolt actions that were real tack drivers. First rifle was a savage 110 in 222 I used full power jacketed for varmints and a lead 55 grn loaded down for squirrels. It was a moa rifle. I have shot 223 in HP matches ARs built for accuracy with fast twist barrels to use 75 and 80 grn bullets again very accurate barrels and the slightly larger volume helps with the heavier bullets. Both can and are very accurate. As has been said for many years the 222 held a lot of records. Its a nice mild mannered round with easy recoil and muzzle blast. They normally shoot very well.