The Towed brake systems come in several types.. A very short primer:
All in one (Example: Brake Buddy, Even Brake) these systems consist of a box that you install in the driver's seat EVERY time you tow... and remove in order to drive.. Advantage.. Easy to move to a new towed car, Dis-advantage: You install them EVERY TIME you tow and store them when you drive.. I do not like them, it is too easy to say "Trip is short, I'll just forget it" also easy to make a mistake when installing.
Air over Hydraulic systems.. Two I know are M&G and Air Force One.. M&G is a air device that fits on the master cylinder. It is 100% transparant.. To go from Drive to Tow you simply plug in the air hose at both ends. To convert to "Drive".. Unplug.
Very nice: Air Force One, as I recall is a piston that hides under the driver seat.. Attach the push rod to the pedal to tow. .Not as nice as the M&G but fits cars the M&G won't.
Stay & Play (SMI) or Unified Brake Decelerator (US-Gear)
These systems are also transparent. Once installed you never need to even look at 'em (Well the controller on US-Gear)
The in-car parts are out of sight and out of the way.
To convert from towed to drive or back.. As I recall on the stay & play you flip a switch
On the US-Gear you plug in or unplug the cable.
IN addition the US-Gear has a set of controls in the motor home, You can apply the brakes manually, overriding the automatic control.. You can adjust the "Gain" so it brakes harder for the same pedal pressure (or softer) and by setting the gain to zero you can completly disable the system (From Automatic control)
That is the same level of control a professional Over the Road Semi driver has over his trailer brakes.
All these systems I've named are progressive: The harder you brake, the harder they brake.. MOST are adjustable as to "Gain" (poroportional) (not the air systems) the US gear from the driver's seat.
Major disadvantage of the transparant systems is you do have to "Install" them (once) and if you trade towed cars you have to Remove them.. Much harder to remove.
But, still, as compared to installing and removing EVERY time you tow.... I"ll take the US-Gear system please.