In the former, household size is presumably smaller and hence, for the same population size, investment in housing and associated infrastructure will have to be higher per capita. Furthermore, the cultural problems associated with first generation migrants are likely to be greater.
Conversely, it is also possible that with higher natural urban population growth there could be greater local resistance to in-migrants giving rise to associated problems in economic and social policy. Thus policy makers also need to give attention to the specific nature of economic demographics in their respective countries as it affects urbanisation.