Question
Should I put all valves in one manifold bank or spread out through the yard?  What are advantages / disadvantages?

Answer
Fnor most smaller yards (less than 1 acre) I think it is best to have a manifold in one location.  Spreading the valves out through the yard involves having a main line and wiring out to each valve.  Unless this is necessary for reasons of hydraulic requirements it is usually more expensive than constructing a manifold and keeping the wiring to a minimum.