I have a prodigy in one truck ( Nissan ) and IBC in the other truck ( Ford ). They both work well, in that they make the trailer brakes work. The Ford IBC is "smoother" in operation, especially at very low speed, I suspect because it releases the trailer brakes progressively ( and gradually ) right before the whole combined rig stops.
I can't say that I feel one system is tremendously superior to the other. They both work to apply the trailer brakes. They both are adjustable so they can be set to be too aggressive, too slack, or "just right". I routinely pull 4 different trailers with these two trucks, and have no problem getting the adjustment right, and get correct stopping from all of them.
EDIT: one further comment. I have found in our Ford ( and I have heard this about GM IBC also, but I have no first hand knowledge of a GM controller ) is that the brake controller is sensitive to making sure all the connections are very good and clean. One of the horse trailers was giving me intermittent operation ( brakes only, the lights were fine ) with the Ford, but then if I hooked the Nissan/prodigy to it, they worked fine. It turned out to be a questionable ground connection on the trailer that apparently the Ford IBC was very sensitive to that flakey ground.
