I have the GHP12 with a Simrad hydraulic drive unit. I already had the drive unit so no need for the Garmin drive unit. We are very happy with ours. The only issue We have experienced is. Faulty rudder sensor cable. It went bad after about 2 years. My own fault as it had a heavier cable resting on it where it connects to the computer. I replaced the $20 cable and it has worked flawlessly for the last 1000 miles.
I would say I do. It like how the cables attach to the Garmin unit. I prefer cables to attach to the side of the computer for compact installation. The Garmin cables attach to the face requiring a larger installation space. Not sure how the ray unit cables attach.
This has been problematic for me on at least one install. Instead of being able to solidly strain relieve them against a bulkhead, and enter from the bottom of the unit, they stick straight out just waiting for an owner to
snag something on them.. My customer actually broke the twist lock mechanism on the housing of the CC but Garmin fixed it for N/C...
If going Garmin just be very careful where you mount the CC..
As for the EVO it really is a nice piece of gear..

Both the actuator box (controls the drive) and the EVO head (course computer/heading sensor) are bottom entrance for the cables. The cables Ray sends you WILL be too short so plan on extra $$$ for that. Also there is no NEMA 0183 backwards comparability unless you buy additional components. You will also need a converter to get to N2K, if you have Garmin or other N2K equipment. Set up is pretty easy on these and unlike the old flux gate compasses does not require motoring in small circles for hours to calibrate the system...
I do think the Garmin drive is a bit more robust but the EVO is a tad more advanced, at least at this point in time.