Can anyone explain the pros and cons between the two? I just built a 700+ hp 540 and would like to keep the gimbal a little safer on my bravo until I get a new hull/drive. I know the full system has it's own hydraulic where the add-on uses your current power-steering system.

I just converted to full hydraulic and will never go back, The steering is so smoooth, no surprises when running. My wife thinks we got a new boat. she said it made all the difference in the world. There is no effort in driving the boat weather it be loading on the trailer or running 90 down the lake.

The add on uses your current cable to signal the steering valve on the inside of the transom to respond external add on ram that is now connected to your drive. If you have slop in the cable you will have a delay in response time of your steering. Full hydraulic is an instantaneous response when the wheel moves. The helm is the steering valve. Going from stock cable to full hydraulic is night and day difference. It was the best thing I ever added to my boat, almost like adding a couple feet to the overall length because of the handling differences. You will not regret it.

I had add on on my Pantera and have a full system to the helm on my AT. The full system is much nicer. The add on was hard to turn at idle and the steering wheel still pulled to one side under load.