Have raced a few vehicles in my day with drum brakes ,never would they pull up in a straight line.! Pedders tests between a rear drum braked Ranger and one with their disc conversion showed a much shorter braking distance.
Never had a problem with disc brakes ,always fit quality pads and discs .
Concede what you say @BJM about straight line braking with drum brakes. Once again all to do with adjustment, braking co-efficiency of brake lining and heat. Discs don't have that problem unless the rotor is warped or caliper/disc pads not parallel to rotor on BOTH sides. Never had any real problem with the drum brakes on my 1965 Valiant which I had from new and still have, but then never subjected to continuous severe use as in racing or heavy towing either! Still has only less than 50 thou wear on rear drums. Front has been changed to ventilated discs with power assist. So all my talk is about my own experiences.
I guess that the test by Pedders would be pretty accurate. But never my intention to push brakes to the limit. The use of gears as they do in trucks/buses on slopes is enough warning for me to go down a couple of cogs when towing. I guess I have been "out-gunned".