From a building standpoint, Sanctum (my furthest back point of reference) was amazing, every town, even dead ones looked cool. From a PVP standpoint, the person with the better gear usually won, it was so one-sided people would run for their lives when they saw someone else.
Zeal had nice towns too, DG however, does not in my opinion.
70% of towns in DG are boxes, or underground apartments like @
zachimon described. Towns in Sanctum were awesome because people were protected by the region that was pvp-off on the whole thing, not protected by walls and a roof/dome.
Zeal, because people were used to Sanctum and getting bearings down, looked nice while also emphasized a new importance on security. DG is just a bunch of paranoid dwarfs living in little cave colonies.
That's why I (with my friends) tore my town's wall down
People need to stop being afraid of other people and PVP, or else this map will get archived and people flying around in creative to see what we have done are just gonna see a bunch of pixel art on shoebox town walls and nothing more. (they won't be able to get inside to see!)