Not my logic, are you going to build a multi storey building without knowing you will have tenants?
Are you going to build six lane roads without analysis of traffic growth?
Be realistic.
Nairobi is dynamic because you need rapid changes, those slums do not depict a modern city. They simply have to go, and from what I've seen above on Kibera photos, indeed you need a face lift badly or rather Nairobi needs a face lift and that is dynamic.
Dar, on the other hand, grows, we have seen growth in Dar during Kikwetes like we have never seen before. It was simply a rush.
When population grows in any city expect infrastructure to grow along with it and that is exactly what we are experiencing in Dar right now, many new buildings, new areas within Dar are emerging. We used to have tall buildings in Dar city center only, now even those areas where we used to say are outskirts of Dar like Ubungo, Kimara, Temeke, Mbezi, and so on and so forth we see huge development with multi storey buildings being erected constantly. We see flyovers coming in different areas, we see huge bridges which cross the sea to cater for city growth.
Be open minded and realistic, dynamic simply means "changes". Growth means expanding.