Smart will do well in depreciation if it matches the Civic. The Prius is the king of maintaining resale. In Colorado, people mysteriously can get 80% of MSRP after 40K miles for a 2004 or newer version. Civics are almost as good, even the non-hybrid models.
Older (1996-2001) 4Runners can be bought used, driven 50K miles, and sold for within $1000 of buying price. They have an intrinsic value that prevents them from dropping to junk prices. Subaru in CO is the same. Audi on the other hand....It is amazing to me that a 2002 A4 that went for $35K new now sells for about the same as a 2002 Subaru Legacy that sold new for $22K. I know a small used dealer that has gone to buying Subarus exclusively, most from neighboring states, and selling them here. He is making a killing.
I'm guessing a dealer that specialized in smart, Fit, Yaris, Elantra and the hybrids would do well.