If you're thinking of an AR for defensive use of whatever sort, what's called muscle memory carries over from any AR to any other AR as far as the operation. That's all reflexive. Grip, sights, trigger: Pretty much the same, allatime. What counts is the training of your mind as to varying situations, different scenarios. Mindset, skill set, tool set--in that order.
+1. Well said.
What is useful about practicing with a .22rf AR is that one is practicing with an AR. The .22rf part is important only because it allows inexpensive practice as well as, noted earlier, practice in places where a .223 is not allowed or appropriate.
Over the life of a firearm, the cost of ammo far exceeds the cost of the weapon; using .22RF ammo cuts that a bit.