Inherent accuracy has always gone to the smaller case. Practical accuracy... depends on the barrel. My advice is to consider your range requirements, and choose with care. If you never shoot more than 300 yards the 223 does it just fine. A fellow shooter has a Savage with accutriger that shoots under an inch at 300 yards all day long.

My personal experience is with two Remington 788's both with Canjar Triggers, T-16 Weaver scopes. Identical except for caliber. The .223 will shoot .3 groups easily, while the .22-250 is more like .4 Both by the way were shot with Sierra 52gr HPBT. Which at the Sacramento Valley Shooting Club is the choice of the small group shooters at anything up to 300 yards. I don't have any experience with it beyond that distance.