Both work well. The Navico PowerWheel replaces your steering helm, which is the logical place to tap into the steering system. The installation is simple, works on a wide variety of boat designs, and the price is affordable. The Autohelm SportPilot Plus installs between your steering wheel and steering helm. It uses a special clutch at the wheel which allows you to steer around obstacles by simply grabbing the wheel.
Installation is very simple, and many of the tools required are included with the pilot.
Small powerboats with hydraulic steering can use one of the smaller hydraulic autopilots. The pump motor simply installs across the hydraulic steering lines and takes over when the Auto button is pressed. A rudder sensor provides information to the autopilot control so that it knows where the rudder is aiming at all times. In general, pump motors can be smaller and power switching circuitry can be more compact with these smaller pilots. Our choice would be the Autohelm ST 5000 or Navico PL-8000.