Colemj, if you are telling me you have had one of the above mentioned autopilots steer you out of a broach or a steering linkage failure at 27 knots in a cruising cat, I am going to have to take your word for it.
We don't do 27kts, and would never do it. Our AP (the one above) steers us out of potential broaches all the time by never getting us into broaching positions. It anticipates these as well as I can, does so longer than I can, and does it at night - where I cannot.
Our AP has also steered us just fine for 24hrs downwind in 35-40kts (reefed to keep the boat at 8kts) with a broken steering linkage, where the only boat control was the rudder with the drive connected. I didn't even know the link had broken - all I remember is thinking that the AP was a bit more active than usual.
These AP's are continually monitoring all instruments and boat performance 100 times per second, and are continually adjusting their steering to suit. They actively avoid jibing downwind, and through rate sensors on 9 axis, they know before hand when a broach is possible and steer away from it. Heck, it even continually optimizes VMG upwind, and can also steer to a polar table. At some point in the above link failure, I'm sure the boat got really squirrely, but the AP almost instantly picked up on that and adjusted the steering parameters to compensate.
BTW, it isn't possible to get out of a steering linkage failure by hand steering - there is no connection of the wheel to the rudders then. The AP is the only hope.
Again, if you haven't used one of these newer AP's, you will be surprised at how much has changed.
Also, see my edit above - I now understand why you linked to the Triton.