I, like many, have had more than my share of jam session G.A.S. discussions, both on this site, and among many working pro associates. The results were the same.
Without knowing what MP was being sampled, the fact is the material of the MP was never reliably nailed by anything approaching a predictable pattern.
Mind you, this is provided it was a truly blind test, which is why I mentioned the perquisite of no preconceived notion of the models being played. And these stage and studio musicians didn't just fall off of the musical "turnip truck" either.
The overwhelming difference, besides the player themselves, is the design and proportions, not the material.
Again, the player's perception of the way a MP sounds to him/her, as well as the feel, playing charactoristics etc. between MP's and the materials they are made of, can impact the player's sound ultimately. But any major differences the listener hears is not a result of the material itself, isolated, making a significant impact above and beyond the core design distinctions.
On a similar note:
This G.A.S. obsessive search for "chops in a box" came into question regarding model/make Saxophone identification in several recent blind sound tests that were conducted on this very forum board.
Given this, the seemingly condescending "Princess and the pea" position regarding a special talent or sensitivity for discerning mouthpiece materials by sound doesn't hold too much water in the real world, spectrum wave analysis or no. A role of the dice gives about the same likelihood of nailing the results accurately with any consistency.
If anyone feels they are getting more jollies for their money by picking a MP based on material and perceived effect on tone alone, more power to you. You pay your money and take your choice.
Anyone hear (pun intended) willing to put their money where their mouth is, and be tested themselves?