User blog comment:DE-Note/What Determines the Strength of One's Aura?/@comment-7622429-20150529163833/@comment-11188061-20150529180546

That's what he meant by quality, dude.

Suppose that a person is untrained, when he takes damage and his Aura will block it in place. The damage taken will be high since the Aura is just a sheen that covers the entire body evenly, like using a steel paper to block a spear. As with  the law of physics, the higher concentration of Aura from the unharmed areas of the body will flow down to cover the spot. At the same time, the body (or the soul?) will attempt to generate more Aura to surround the body to regain the natural equilibrium it has before.

As compared to the warrior who focuses his Aura to defend only the vital areas, and to minimize useless shielding on areas that are highly unlikely to be attacked. When attacking Aura is focused naturally onto the tip/surface area of the strike to achieve maximum damage. Same goes with defense, although only at areas that are unprotected by armor. In Pyrrha's case perhaps she only needs to coat her shield with minimum Aura to make it a super tough, mostly impenetrable defense.

In fact, at its perfection the Aura should automatically distribute themselves as such at all times, even when they're asleep. With long enough training, it should stay that way and never 'revert' back to its old state unless the host (and now it sounds as if the Aura is a separate living entity!) suffers terrible damage or shock, thus forcing the Aura to be reduced or focused on somewhere else to heal the host.

As a result Aura is used up in a far more efficient manner. Regeneration will still happen (in fact you want it to) but it'll ideally match or outmatch the rate of damage taken, and at that point the only defining factor between two evenly matched opponents is their will.