In the fluid power world we are mainly pumping hydraulic oil, with three basic types of pumps; gear, vane and piston, while they all produce the same effect, (they move fluid), how and why they get applied are distinctly different.
It used to be a relatively easy selection based on the price. A gear pump was the least expensive, followed by the vane pump and the piston pump. Today the dividing line between all three can be blurred and not so easily defined. So which do you choose? Where to begin? Should we look for the least expensive or the most features?