Rob Pincus explains the advantages of a muzzle low ready position, especially in an extreme close quarters situation. The low ready position allows for more efficiency and consistency when moving into a shooting position and for dramatically more control if your rifle is ever grabbed by an attacker.
Ankle Holsters offer one unique advantage for defensive firearms carry, as they place your defensive tool in a location that most people do not think to look. Danny Pieratti prefers ankle carry and demonstrates proper presentation from that position in this video.
Student alert! If your defensive firearms instructor is not giving you an integrated system of firearm manipulation techniques but rather a set of unconnected techniques that don't integrate well together, don't reinforce each other, and don't contribute to your efficiency by being consistent with one another, you need to challenge those techniques.