What is the best system of local government to operate our cities why?
There is no objective way to say which system of government is best. Different systems may work better in different circumstances.
For example, I would argue that a council-manager system of government is good for small cities. This system ensures that such towns (which do not have big enough governments to warrant full-time mayors and council members, will have a professional running their city operations. The council provides democratic control and the city manager provides competence.
By contrast, a strong mayor system is probably best for a big city. In such big cities, government is much more important to daily life. It would be dangerous, politically, to have a chief executive who was not elected by the people. Thus, a more elected system is better in such cases.