I think the most telling point is that it is never the equipment makers who go on about how their gear sounds so much better than another maker, or even within their own product line. They just list the specs, and the things they've done which are supposed to improve the sound. It is left to the consumers and the reviewers to express the words about how much more chocolaty this new fooswuzzle is than its nearest competitor.
The few companies which do spout superlatives about their products are the ones I just seem to reflexively avoid because their claims seem so outrageous.
Good point, most of the claims aren't actually coming from the manufacturers, although they are stand to benefit the most.
So does it all come back to the consumers & reviewers hearing what they want or think they should hear? Have they simply been influenced by what they see and read?
I wish someone would do a proper test and help put this issue to rest, but I don't think the manufacturers and dealers would like it.