I suspect they are much, much larger than most pre-existing stations. Since the Nauvoo/Medina Station probably was one of the begins ships ever made previously and looked to be at least 4 times as big as Tycho Station, but still probably only housed in the tens of thousands at most, you can imagine the much larger scale of a void city.

The real question is how could they build void cities in what seemed like a short time frame.