I've used the time-based (Reese Brakeman II), inertial (Tekonsha Sentinel) and true proportional (Jordan Ultima 2020), and the Jordan is head and shoulders above the others.
Since I bought the Jordan, the BrakeSmart controller has come into the market. It's intrusive (it taps into the brake system hydraulics) and more expensive (more than double the price of the Jordan), but it has the potential to be the best out there. I'm waiting for some feedback from Ken Lenger and others who have used the Jordan and are switching over to the BrakeSmart before I make the jump from the Jordan, which works just fine!
Rusty