We have an older Raymarine hydraulic autopilot. It's basically a contol panel a fluxgate compass and a hydraulic pump. The unit is at least 15 years old and works flawlessly. The pump seems to be very robustly put together and there is no evidence of any leak problems. Our unit was made before there were interfaces to GPS units -- in fact it was made before GPS became a common feature on pleasure boats so all it does is hold a pre-set course. This it does very well under both power and sail (though we rarely use it while sailing.
If I were replacing this unit I would probably check for recent reviews online and in Practical Sailor but you've probably already done that. After that -- assuming the all cost about the same -- I'd go with one that was easiest to interface with my plotters and other instruments.
Sufficient unto the day is the evil thereof
S/V Enchantress -- Morgan 45