.223 vs .308 here we go again...
It all depends on how, when, and where you plan on using your rifle.
If you want a home defense rifle, both are overkill unless you live on some country ranch with many acres open property. In which case, the .308 might make more sense to some.
If you want to hunt prarie dogs, .308 is overkill. If you want to hunt something bigger than a coyote, .223 may be inadequate.
If you want to imagine a survival scenario, there are pro/cons for both:
.223
pros: lighter weight, carry more rounds, vast availability, DOA (dead on arrival)
cons: designed to maim, delflected by brush unless using steel core
.308
pros: better first shot hits that will count, better penetration thru vegetation, good availabilty, DRT (dead right there)
cons: heavier weight, carry less rounds
As far your question regarding .223 accuracy, this should be irrelevant. Accuracy varies more between weapon systems than between calibers. AR15 type rifles are very accurate semi-automatics in either caliber.