I think there is something to be said for small maps, especially if there are defined regions in the town. i.e. a port, a slums, etc... It also helps give the feeling that it isn't just a big square. It also separates the workload so that it seems like you are getting more done each time you do the mapping for a region, and it's easier to look at each region individually and correct for mistakes that might be overlooked in a larger map. So I think small maps can be better, especially for large cities