We are specifying 84" x 144" sluice gates in one of our projects and we expect very high torque and thrust required for the actuator to pull up the gate valve under a head of 40ft water.
Speed can be an important spec.  Electrics usually operate at only 12-15" per minute.  If this stroke is 144", it might take 10 minutes to open.  Likewise, if there is a power failure it may be necessary to maintain control of the valve.  A hydraulic accumulator can handle multiple strokes after power is lost.  This accumulator would push fluid into the hydraulic actuator.
However, hydraulic actuators can be tall.  If there is a height issue, electrics may be the way to go.
Valid point. However we do not know the actual operating speed and only know that it does not have to be fast; since the gate is operating rarely upon plant shut down or startup.
Hydraulic actuators are not allowed in most water treatment application because of the possibility of contamination and housekeeping considerations. Therefore we are bound to use electric actuators.

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