"Reliability maybe, sound quality? I bet if you didnt drive them into
clipping
you would not hear the difference. In fact under many tests I have seen
performed the measurable differences were below the threshold of human
hearing."

A good example can be shown in carsound.com's reviews section. If you look
at one of the amps that Pug cited as "bad" (Jensen) and compare it to one
that he cited as "good" (Zapco), you'll see in the charts that the THD
measurement on the zapco was greater.

http://www.carsound.com/reviews/amps/ag1000chts.html

http://www.carsound.com/reviews/amps/ats50rxchts.html

But, as you've pointed out already, nobody's going to hear the difference
between 0.05% and 0.2% THD anyway.