I can't speak to other brands, but chose Trac stabilizers from American Bow Thruster for my boat. I looked at the Mitsubishi gyro, but the energy requirements, cost, spool up time, space requirement and less effective roll dampening outweighed the advantage of no hull penetrations, which is a significant advantage for sure.
An air system is an interesting twist on proven technology, but I'm not sure why a solution needs to exist where there may not actually be a problem. Perhaps this is why there are not that many installs?
Hydraulic systems are dead reliable and I think there is a reason why they are viewed as the standard for many tasks on a vessel. Once you have the hydraulic system for the fins, you also have it for other motors, like winches, thrusters, windlasses, high pressure washdown pumps, etc.
I didn't know it at the time I made the purchase decision, but the service I have received from Trac is pretty much off the charts. They really do set the standard that no other company I have worked with could better. They are more engineering geeks than sales people, so seem to approach an installation from the standpoint of how best to accomplish the task rather than selling the client. I couldn't recommend them more highly.
In the Puget Sound region Platypus Marine in Port Angeles, Latitude Marine in La Conner and Bracewell Boatworks in the Vancouver area would be on my list of firms to get a quote from. I have worked with each, and all are capable of doing what needs to be done in a professional manner. If you want a PM on strengths and weaknesses of these companies (they each have some of both), I would be happy to send it to you.