John:

I have used both a Raymarine ST6000 with a rotary electric drive and a
Simrad/Robertson AP11 with a hydraulic drive. There was no significant
difference in power consumption. The hydraulic drive (with an integral pump)
only runs the pump when it needs to. If I watch the ammeter, I see about 1-2
amps normally and it jumps up to 3-5 amps when the pump kicks in. The linear
electric drive does about the same.

In general, hyraulic pumps and cylinders are pretty robust and probably are
less prone to failure. As others have said, with the hydraulic system
disengaged, there is very little drag on your steering. Mounting a self
contained hydraulic actuator is no different than a linear electric
actuator.

The Raymarine has a better user interface and I think, a better algorithm
for dealing with various sea states and imbalanced helm conditions.

So my vote would be Raymarine electronics with a hydraulic actuator.

David