Call me "Old Lady With Lots of Shuffles" - they are all aluminum and all durable as all get-out. I own two refurbs and they look as good as the one I purchased brand new (and work at least as well, besides.).
I tend to think of the grey aluminum ones as the classic Model T - best suited to the classic type of people who couldn't care less about showing off or "making a statement". They're the genteel old money of the shuffle owners.