Its impossible for a few to represent the interest of many. So the simpler the choice, the less representative it is. It should be more important to give power to the person running your city than your country, because his policies are way more likely to make an impact in your daily life. Making a oversimplifying comparison, centralization is usually against the robustness and efficiency of a system, since it adds a central point of failure. In practice, for me, it add so many layers of abstraction that the ones at the top make decisions on things very different than what the ones at the bottom care about.

Centralization was practical before, but now with technology we have an increased capacity of descentralization.