Ball valves have smooth edges, conducive to one smooth flow path. Butterfly valves have a cutting edge, splitting the flow and providing a catch point surface. Gate valves on the otherhand provide finer tuning...
That's why butterfly valves are poor for regulating flow from a higher-pressure pump - they tend to wear and leak. I don't think a March pump would cause issues though.
They do have to be a LOT easier to clean than ball valves. Tom - have you used the new valves yet?
I don't think you could keep a gate valve clean/sanitary.