... I would prefer the GMT for one reason: Withour reading glasses, I would be unable to read the second time zone on the Sky Dweller: It consists of a ring of numbers rotating, so I HAVE to recognize the number in order to know which time it is elsewhere. On the GMT, I have a hand, and even without reading the figures, the position of the hand alone is indication enough for interpretation.
Other than that, the Sky Dweller is more luxurious, less ubiquitous and has the more interesting complication. I love annual calendars.
Marcus