I will discuss a few systems and let you decide
Ready Brake (Also Blue Ox Auto Stop)
These are surge brakes. As the Towed tries to push the RV they apply the towed brakes, Other than initial set up fully automatic. but be sure to read the forums about them as there can be issues. (NOTE this applies to all systems). These do not use towed vehicle battery.
Advantage: Once it is set up you should never need to adjust
Disadvantage: The cable on the car is like the parking brake cable.. It can size up and cost you a brake job if you don't check it.
System in a box in the driver's seat (Brake buddy, Even brake, Apollo)
These systems claim "NO INSTALLATION" but the truth is you install them EVERY time you tow, and remove when you drive
Advantage: If you have a "Stable" of towed cars. One system works in all.
Disadvantages: You have to install and every install is a chance to screw it up like the dealer did mine (Different system though) Or other screw up
Disadvantage: You have to store it when not towing
Disadvantage: "Oh it's only a few miles.. I'll just forget it for this CRASH Wish I'd remembered"
Disadvantage: These DO use towed vehicle battery.
INvisi brake: (or invisible brake) 100% Transparant to driver of towed. Once installed NO connections *(Save for break-away)* Nothing to forget.. Just plug in the light connection.
This system uses towed vehicle battery but provides a means to re-charge from Tow vehicle.
US-Gear Unified Brake Decelerator: One additional electrical connection (Hard to forget)
Most control of ANY system same level of control in fact as a professional OTR semi driver has over his trailer brakes,, You can set, or disable the trailer brakes (Towed = Trailer) from the operator's seat and you can set them either automatically or manually INDEPENDENT of tow vehicle brakes.. This is the system the dealer screwed up on my Towed, cost me a brake job.
This system uses towed vehicle battery but provides a means to re-charge from Tow vehicle.
I think it' M&G (This is an air brake system) If your tow vehicle has air brakes this installs between the brake booster and the brake master cylinder on your towed.. Again, other than the air line and the break away nothing to do when you hook up save hook up. So hard to forget. Uses NO battery power at all. All air powered.
My recommendations are the M&G if you can use it and have air brakes
Then all systems OTHER than the box in the driver's seat.