Wow. This thread had plowed its own track. I guess I was the primary hijacker, so "Sorry, Melissa."
I'll add this:
Although I don't think the type or lack of plating could possibly make much difference in the sound of a sax, it does apparently make some difference in the necks. I've read of many pro players trying all the silver, copper, bare, gold and lacquered neck options on new horns. I think this is a common passtime at professional trade shows. There apparently is some noticable difference there.
There apparently is some difference, too, in the type of base metal used in horn bodies, ie, solid silver or copper instead of brass. But, again, I can't imagine this being that big of a deal, unless maybe you're putting together a matching horn section for orchestral work or something. (Personally, I think it's an excuse for horn makers to sell some really, really expensive horns).
I also believe, but couldn't prove, that the tone of a horn improves over the years as it's used, or possibly simply as the brass gets older. Like I said, can't prove it.
Certainly, for the common player, none of these factors should be important, as the weakest link in the tone chain is obviously the reed/mouthpiece. Once you've got a horn you like in good working order, that's the area the player should concentrate on as he strives to produce decent tone on a consistent basis, IMO.