Nathan, the top two, IMO, look best. I would favor the night version, but do as you wish, because you have the full intent and vision for this illustration. One warning: that spaceship is perfectly halfway between the people and the city (and that makes the composition look odd). Push it further in the distance (scale it down and move it left) -- that's what I suggest (or maybe you don't need it?). Watch out for all the straight lines in the composition too. If it's organic, it's usually wavy, knotty, or accidental lines. Good luck!