As far as I can tell, the Shimano Road and Mountain disc rotors are functionally close enough that I wouldn't be able to feel a difference - so between the two, I'd likely pick based on aesthetics or availability, provided the cost were similar.
But part of me had been wondering if Shimano IceTech really was the best, and if there were any other rotors (cool looking or not) that would offer measurably better braking performance or resistance to warping, that were in the same price range. SRAM Centerlines have a cool aesthetic, and Hope rotors have the option for anodized carriers, but not switching if their performance is worse with Ultegra calipers.