I think everyone envisions Mars as harder than the South Pole. The reason people like Elon envision colonizing Mars instead of the South Pole is that they posit a big prize for succeeding at the former (becoming the emperor of a large, viable landmass, out of range of other nation-states' control and blast radius) but not the latter.

(I think this is an accurate observation of motives, but I disagree with the posit.)