I'm with Steve on this one. Besides the points he's mentioned, arctic cold can freeze your coolant and crack an engine block, and it's also hard on bearings, seals, suspension, plastics (they warp and crack), and every other part. When I lived in North Dakota, where ambient temperatures reach -40F for extended periods, I'd jump in my car in the morning and even though the engine had been plugged in all night everything else was hard as a rock. The shocks were frozen solid, the tires had flat spots, even the foam in the seats was frozen solid....it was like sitting on a marble bench. And we used to view used cars differently there than we do in NH. In NH we look carefullyy for rust. North Dakota is too cold for salt to work, so they use sand. Used cars can look perfect but be totally shot mechanically.
IMHO extreme cold is definitely harder on a car. And I speak from painful experience.