Shipwrights thrusters operating at 50 hp very often are not audible in the pilot house. There is less flexibility in the design of the hydraulic system because hydraulic motor thrusters 'lock in' the size of the hydraulic motor. This can have more serious consequences which might not be obvious. Typically hydraulic motor thrusters work at low pressures and high flow rates resulting in large hoses and large reservoirs. Large hoses lead to difficult routing during installation as well as much more space being used in the bilge.
Large reservoirs waste valuable engine room space.
Equipment necessary to handle large flows is much heavier and bulkier, making it more dificult to install and service.