The best hydraulic pump design is the one that is most appropriate for your application. The reason that there are so many pump designs is because manufacturers or designers felt there was a need or a market for their particular design of pump.
If you are creating something simple, such as a hoist in an automotive repair shop, a little tiny gear pumps that might cost you $50—and it would do the job well. There’s no point in having a large displacement, variable displacement piston pump in that type of application.
However, if you are running a brand new injection molding machine, you may need some advanced hydraulics pumps that have allow for control of the displacement, pressure and flow. Feedback and really advanced controls that allow these machines to have the highest performance percentage amount of efficiency.
It all depends on your application. There’s no one pump for every application. It all depends on what you’re looking for—and what your budget is as well.