I don't know about either rifle. I've heard, but don't know, that Savage woud be the most accurate.
What I do know, is there is not advantage to the extra 4 in barrel on with a 223. The most accurate in that cal would be in the 18 - 20 range. That is unless you are planning on using iron sights. Then the extra sight radius would be an advantage.
The Mann accuracy device that the Army uses to test ammo for the 5.56/223 is right at 18 inches.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071