I had an unpleasant experience with a horse trailer with surge brakes on ice. Going down a hill the trailer pushed enough to lock the trailer brakes. It pushed into traffic to a 90 degree angle and stayed there until I started up the other side of the hill. The initial speed was about 15 mph. I had to speed up to keep it from going all the way around. At least with electric brakes the sensitivity is adjustable and the trailer brakes can be used independent of the tow vehicles brakes, very helpful if high speed swaying occurs.