Why do I like Class AB better than Class A?

Mrtennis, you can expect most transistor amps to be somewhat bright and lacking bass on most full-range ESLs like the Quad ESL 63.

The impedance curve of such speakers and the way they operate simply does not favor most transistor designs. there is more information at this link:
http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php

I also almost always prefer AB to pure class A. I do love my my Reimyo PAT 777 but it was purchased specifically to drive the ribbon teeters in my self designed 3 way active speakers. Push pull simply sounds more focused, and real in most cases to my ears. Now I do remember loving a pair of Aleph 1.2' I had in my possession briefly about 17 years ago with a set of Miller modified Infinity RS1-b panels I used to own and that combination was STUNNING (on certain types of music). No saxophone and the Emit drivers were subject to resonances that destroyed the sound :(

That would depend on the amp, preamp and speakers.

I had the Plinius a few years ago and preferred listening in AB mode most of the time. For rock or more dynamic music AB overall sounded better and more accurate. I agree with the original poster it sounded bloated and a bit fuzzy. For softer sounding music like classical or Jazz I could see where Class A would be preferred.

I would trade it in for a Sugden.