Mwanza is bigger to Nakuru because of its population and economy, with gold aside, you'll still remain with cotton and fabrics manufacturing, fish processing plants, meat processing plants as cattle business is thriving. BTW Tanzania is 2nd in Africa and 11th in the world with more livestock.
And what does Kinshasa produces and Dar can't? Is it hotels, housing, getaway to the world, communication, banking, roads, mass transit or maybe clean air and water. Strangely enough, non of you is taking about Nakuru which is the name headlining the thread.