here's my attempt at a semi-laymen view of the issue.
with Class A, a single output device (eg, transistor) produces the full output wave. That is, both + and - side of the sound wave.
with Class AB, the + side of the wave, and - side are produced by 2 separate output devices.
The result is Class A generally produces more coherent sound because the 2 waves in Class AB don't always match up perfectly resulting in "crossover distortion". Further, Class A is less efficient, and generates more heat because of the way the output devices need to be biased to operate in Class A. Conversely, Class AB is more efficient to operate, and to manufacture (all other things being equal).
with Class A, a single output device (eg, transistor) produces the full output wave. That is, both + and - side of the sound wave.
with Class AB, the + side of the wave, and - side are produced by 2 separate output devices.
The result is Class A generally produces more coherent sound because the 2 waves in Class AB don't always match up perfectly resulting in "crossover distortion". Further, Class A is less efficient, and generates more heat because of the way the output devices need to be biased to operate in Class A. Conversely, Class AB is more efficient to operate, and to manufacture (all other things being equal).