Yeah, I debated breaking down the word "corrodes" at the time I typed that, almost did, then decided I get pedantic about such things too often anyway, so just went with the bottom line short version.
Sterling silver and nickel DO both corrode, of course---that's what the whole "turning black over time" thing is---they just do it in a gentlemanly way. Very shallow, and easily removed.
Brass and copper---especially copper---can get truly nasty. Depends on storage conditions, humidity, etc., but if you've ever seen a pipe with a runaway copper band, you'd never use one. Blooming, turquoise-colored crystal sludgey stuff growing on it like a mushroom. Brass is definitely less reactive, but can still get pretty ugly.
Anyway, there's (effectively) no cost or labor difference between the candidate metals, so using the industry standards makes the most sense imo.
I'm not sure what was up with the nasty nickel you've seen, mawnansmiff. Sounds interesting. Pretty much any alloy that's not true silver was/is referred to as "nickel" by the old pipe making outfits---sometimes as "German Silver"---but no one knows what it actually is. Peterson's is a respectable company and always has been, though, so wouldn't be using a junk alloy to save a penny. Again, interesting. I wish I could see what you saw.
Speaking of bands, there absolutely ARE fake silver bands out there, so beware when stocking up, Nevadablue. I have a box full of them. :lol: Clearly stamped .925 Sterling, and absolutely anything but.