Omogeneous vs Heterogeneous Ethnic Compositions: Which type of nation prospers above the other?

This is my research paper and is due for my exam grade this semester. My research topic is which type of nations prospers above the other, a nation with a Homogeneous ethnic composition or a heterogeneous ethnic composition. This essay should be one sided so please argue in favor of a Homogeneous nation, HOWEVER in the essay you have to have some exploration into the other side(Heterogeneous) then coming back to the side I like(Homogeneous). You MUST be able to support with credible facts on both sides. When I say which type of nations prospers above the other, I mean economically, socially, etc. Please if you would include and outline to this research paper that is organized in the logical progression of ideas in the paper. The outline must allow for refutation of intended response, and your ideas to link directly to subject.
Thank you and if you have any questions please contact me! If this is done right then I will leave incredible feedback!