I don't think your atmosphere comparison is valid. The moon has absolutely no atmosphere. Mars' is 1% of earth. That's still a lot of _something_. aerobraking, and easy access to unlimited CO2 is incredibly valuable. Delta-v to mars is less than the moon so the extra solar panels required is not that big of an issue. The moon will probably only be a research outpost because of its gravity and slow rotation. Mars on the other hand will most likely transition to nuclear eventually to sustain a city/colony and industry