Atmasphere, do you think the differences could be measured someday, but we have not figured it out yet?We can measure them now, but we don't go about it right.
Essentially what is needed is a weighting system; one that applies more importance to the higher ordered harmonics since the ear is so much more sensitive to them and places less weight on the lower orders since the ear doesn't care about them so much. Then the spec sheet can tell us how the equipment sounds.
Horrors!
The industry is a long ways away from that right now. The way our ears detect sound pressure is sort of an inconvenient truth. Easy enough to prove though and with really simple test equipment...