In order to make hydraulic stabilization systems work effectively at ‘zero speed’, huge fins need to protrude from both sides of a vessel hull.
A large hydraulic pump moves the fins to stabilize the vessel. The pumping speed may change frequently depending on the situation, which may result in random load variance and require a larger generator.
On the other hand, the power input required for ARG is steady, reducing the demand for power supply. The entire unit (incl. gyro and driver) stays inside the vessel, which makes docking and maneuvering easier. It is even possible to run your ARG at the dock while using the shore power.