I’d say a flute’s sound and feel is about 75 percent embouchre: size, cut, chimney depth, shape etc. 22 percent design: tone holes, bore, lined unlined etc and maybe 3 percent material: delrin wood etc.
anyone trying to tell you any different is daft or trying to sell you something
Personally, I think a flutes sound is about 75% player, 24% embouchure/tones holes/bore, and 1% material, but from a player’s perspective I do think it’s important how you feel about the material and the flute, which can impact sound by how much you like the flute. You will not sound as good on an instrument you don’t like regardless of the reason.
Eric
If you can count past tense, Tom Doorley played a Delrin Seery to smashing effect (IMHO) throughout his first three Danú albums. Of course he went on to wood, but tonewise I didn’t find anything appreciably lacking before that.
I’m of the opinion that material does make a difference, e.g. boxwood is distinctive against say cocus.
Re a blind test (for a listener) to tell delrin from wood. A good player would be able to change the natural tonality so that one would sound like the other. OTOH there is probably a question of degree. If played to really bring out to the full rich ‘woody-ness’ the wood might have a very small difference that the delrin could not reach but I would expect it to be minimal. Maybe the derin would have to be played a little softer to avoid some of its normal tendencies when trying to bring out the richest of ‘wood’ sound from it? Like most of us I’ve never had the same flute made in wood and delrin to compare but Loren has so I value Loren’s view. I have played plenty wood and have a delrin (and wood flutes).
While it’s tempting to suggest Joanie Madden, I’d guess you’ll argue that either she’s not a top flute player or it’s not the same…
But (silver Boehm flutes apart) what of the oboe and clarinet worlds? While I’ve no statistics to back this up, I’d also guess that resins and ebonite are far more widely accepted among their top players. And how about these eighteenth/nineteenth century ivory flutes? Did those who tried or commissioned them say ‘hmmm, I’m not sure about the molecular structure… it’s just not wood’ or ‘wow, an ivory flute!’?
My numbers are from a players perspective, jayhawk.
Listeners perspective, I might go higher than your 75 percent player mark!
While I’m with you and Loren here, might be worth adding that you could (probably would!) also get the ‘same’ flute made of the ‘same’ wood and find it different…
I agree with you fully, Peter. Even fully machined items like Tin Whistles can play differently, so hand made instruments are much more likely to vary instrument to instrument.
Eric
After years of fighting the wood-over-delrin battle, most frequently on the wood-is-better side, I’ve come to the conclusion that a well-made flute will sound good in the right hands regardless of the material used. I’ve played enough good Delrin flutes at this point that were easily comparable to wooden ones, and better than many, to have given up my gut-instinct bias against polymers.
That said, I also believe, as many others have said, that our personal relationships with our flutes - which often means the feel of it in our hands - contributes a lot to our perceptions of a flute, and undoubtedly to the performance on it.
Yes, and no. And kind of. 
Same wind instruments of the materials can vary slightly to be sure due to slight differences in the hand made nature of the instrument, and also due to different wood densities, as the density can vary a bit from one piece of wood to another, even of the same type. But at the same time, different woods still sound different from one another. I used to work in a recorder and flute making shop and I literally heard instruments being played all day long, for years. Boxwood, Blackwood, Rosewood, etc., even solid ivory. While one blackwood instrument can sound different from another blackwood instrument, a boxwood instrument will sound more different. This is hard to describe but it’s true. Well, at least that has been my experience.