Does the big (0.012 Earth masses) Moon of Earth clear away NEAs, Earth orbit crossing asteroids, in a significant way? Venus and Mars don't have large moons, do they therefore have larger or smaller population of near asteroids than Earth would have if it were in the same orbit?
The outer planets have large moons, but also lots of captured asteroids, trojans and centaurs. Does a large moon even help gathering such objects, rather than ejecting them? Moonless Mercury and Venus seem to be pretty clean.