I won't get into the chemistry of the issue, but the short answer is that the previous poster is correct; you can get spangle either way. I buy about 10,000 sheets of galvanized metal a year and some has spangle (in varying sizes) and some does not. Even the largest spangle we get now isn't quite as big as the stuff from 30-40 years ago but it still has noticeable spangle and would likely suit your purposes fine.
You won't be able to order what you want; go to a large sheet metal shop and ask to see the metal and pick something you like.
Dave