[KenWittlief]

Im not sure I understand why people are saying pneumatics are rough, and hydraulics would be smoother?

Pneumatics use air, which will compress. Pneumatic cylinders act like adjustable air shocks, or air springs.

Hydraulics use oil, which is un-compressible. When you extend a hydraulic piston to a certain position it will be rock solid and will have zero give.

With hydraulic valves you can let small rates of fluid through - they are proportional valves, but you can also let large amounts of fluid at high pressure through, and send very violent jerks into the chair someone is sitting in.