I don’t find a significant difference in sound, in whether or not a whistle is nickel plated; the thickness being the main factor. But, to me it seems like polished nickel is a bit slick, and a little odd to play upon. Now I’ve had nickel from early on, but to me it seems that way. Perhaps wood or brushed metal is easiest in that respect, but I do like the looks of polished brass or nickel.
What do you think?
In the past, I would have said flat out that nickel, especially thick nickel, was the best tone-wise. However, recently having purchased a Clare which is brass, and not all that thick brass at that - I’d say it’s “medium thick”, it also has a lovely sound. However, a I had LBW that I really disliked the tone of the tube (the head now resides on a nickel gen body) which was a thin aluminum.
My guess is that nickel vs. brass isn’t as important as maker design. I also think there is a minimum thickness of any material for the tone I like.
Eric
Walden, this once a poll would have been good. Mmmmh.
Everybody: come vote in my thread. 
Yeah. Okay. I’ll go cast my vote, and try and avoid dimpling or hanging any chads.