I am doing this circuit that has 15 pic controllers that control proportional valves with PWM....Am I better off having 15 small regulators or one really big one?
My preference, for efficiency of parts and design effort, would be to invest in a single supply and make it to the appropriate specs (voltage, amps, ripple, and so on).
In some cases, for remote loads, a main DC supply is used (switching type if you want good efficiency) generating a voltage output slightly above the desired voltage with a low-dropout linear regulator at each load point to give good local regulation and decoupling of the power.