I like my tekonsha Voyager. Older design, supposed to be proportional. Four wires, one light, manual proportional apply and two knobs (sensitivity and gain). Works well and is like $30 for a used unit as long as your not changing trailer/load constantly it works pretty well. Advance Auto sells a unit about $100 that's proportional and digital display. Good if you got multiple trailers. Can adjust gain and sensitivity by number. (Write it down for each combo). Proportional = harder you brake, harder it applies. (Most use internal accelerometer plus a microcontroller tied with the settings to output a pwm signal) the one from advance does not apply brakes unless it's actually receiving G Force input. (But has manual override as well)
