While the world of .22 accuracy is now dominated by the ppc's and such, when the .223 came along, the bench crowd found it wasn't as accurate as the .222. But the difference was not significant in the real world.
A fellow would have to be a much better shooter than me to tell the difference. And I own rifles for both cartridges.
Considering that you can get 1000's of once fired GI cases for very little and surplus ammo for pennies, the .223 is the way to go if you're a varminter or a "friendly" paper puncher.