NEMA connections are relatively simple so brand is generally meaningless...unless so far out of generation, mixing may be a problem...even with the same manufacturer. Just check NEMA sentence requirements.
Hydraulic pumps are universal at least for all the APs I have installed...right size and power, good to go no matter the source.
So the compass, rudder indicator and "brain" are easier if all the same brand but even they can be mixed and matched if you are willing to do the work.
Robertson (SIMRAD) APs reigned supreme for many years...but now most do the job just fine. I have been to/from Florida many times on Raymarine pilots...easily over 20,000 miles on them without even a burp. The best? Heck no but who is? In my mind any one of them that works fine for you and fits your budget is the correct one.
Most people never use much more than auto to steer a course or track to GOTO a waypoint/follow a route.
All the fancy search patterns and trolling patterns and other bells and whistles may be useful to someone...but I would say most never use other than the basic features.