Why would anyone want class AB amp when class A always sounds better ?

People with blood type A are always better than ones with blood type AB. What???? A nonsensical statement but assured to arouse a response.

Class A runs very hot and very inefficient , big watts in pure class A is big bucks

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And when one's listening room is located in say Here in New Orleans, or Phoenix, or  South Florida, , the heat factor of a  class A amplifier is a  important consideration.
 The  Defy7 is like, I think Richard Gray says more like class B,  throws off  less that I had anticipated/with 12 tubes. 
, Richard also prefers Class A.
 But as you mention, Big Bucks. 
Did you say very inefficient?
Oh I see , requires plenty of power current = heat.
Glad the Defy is not class A. the heat  radiation would be too much to deal with in my 10x12 listening room. 

Im not sure what I'm missing, as in, who cares how efficient an amp is.  Are any of us concerned with how much power we consume while listening to music.?? We spend zillions to achieve the best sound on components speaker etc,  power is pennies compared to what i spent on speakers.  Same with heat . So What.   Ive got 4 tons of ac so bust out the marshmellows.  ive never understood why people bring those up when what we are going for is sound.

"The difference you hear with more/higher Class-A bias, is an easier, smoother, richer presentation to the sound, that’s no less dynamic and yet makes the speakers disappear, even as the music goes louder. And as a result the sound washes over you rather than being fired at you from the drivers, and that is the result of the lessening of the class-B xover distortion when you engage more and more Class-A bias."

That has been my experience as well. I experimented with various bias currents in my Integrated Amp and the sound quality improved considerably with higher values. The music had more body with a richer midrange, which was quite noticeable at low (SPL) listening levels. Nelson Pass talks about this in his "Leaving Class A" article.

the listener has final word. 
My amps will stand up to many class A amps. 
So will my Sunfire 600 sig at class H.