About ten years ago I helped Manitowoc, a major US manufacturer of ice-making equipment, to convert their exterior panels to 201 with a finish rolled onto a bright-annealed surafce by a temper mill to resemble #4 polish.   (Trade name,Koolline) Previously they had used 304 with a #4 polish. Today I saw one of these units outside a beach side restaurant in the Caribbean. It was under an roof, so deprived of cleansing rainwater. Despite the sea salt environment, there was no surface except some superficial staining on a leeward side.
I have seen worse corrosion inside a McDonald's in Pittsburgh. This should help people who are worried about switching to 201 from 304. I had the same experience with gasoline pumps under roofs where 304 #4 was showing rust. After changing to a bright annealed finish there was no rust. The lesson is:
 Watch the surface finish, not just the alloy content. Surface finish is more important when ambient environments are concerned.