The maxbrake controller is not a "hydraulically actuated" controller, it is completely electric inside, no slave cylinder or brake lines to deal with. It does however use a pressure sending unit that you install in the brake system, then electrically translates pressure to braking effort.
Look at it this way, the inertia type tries to guess how much you want to slow down by measuring how much a pendulum swings inside the box, which varies if you are on a hill. They work OK, but not perfect in all situations.
The maxbrake brake applies trailer brakes in direct relation to how much you step on the pedal, and the ratio is adjustable for a light or heavy trailer, this should result in more consistent application of the trailer brakes in most situations.
Again, I haven't tried one yet, but I like the idea.
I've used the inertia type, and they work but aren't anything to brag about.
Most recently I've used the integral brake controller in a newer ford pickup, which works very similar if not the same as the maxbrake controller. The ford controller is quite nice, very steady, predictable, and adjustable, I hope the max brake controller is as nice or better.
Grigg
