First, you'll need to confirm whether the 5.56mm (.223) is a legal big game round in your state.

Second, there are quite a number of AR variations. Typically, a shorter barrel is "handier" in a home defense scenario, but the caliber itself may not be the best choice if you live in close proximity to others (i.e. apartment, housing development, etc.)

Sighting systems might also be an issue, as the laser or electronic sight you may choose for a defensive weapon may not be legal for hunting.

Have fun shopping - there are plenty of rifles and styles (as well as accessories) to choose from.