If the problem is that you want to enforce common minimum standards, improve transparency and training, my guess is that this would be easier to achieve on the more centralized end of the spectrum. If your goal is to maximize the dispersion of power to the local level, go ahead and give every community its own independently run police organization. To a certain extend these goals are in conflict with each other and you have to decide where your priorities are, would be my intuitive sense. For me personally, I feel most comfortable with a system where the police (who are carrying guns and are under certain circumstances entitled to shoot me) is run by institutions that have at least the theoretical capacity to properly finance, run and train those forces and which at the same time have a modicum of accountability to me. In my view that would be state governments, certainly not municipalities.