My answer is based upon my experience; some of it being extensive experience with high loads being absorbed through the braking system, also with little room for compromise for doing so would have (potentially) meant crashing into a solid object at speed, on more than one occasion.
My vote is for disk brakes with the largest diameter disk rotor currently available to be fitted to the front wheel as the only sensible option if using a motorized bicycle.
Some will disagree with me, but hey, i'm only voicing my opinion from past experience with rim brakes and disk brakes; the former being dangerously unsafe under certain riding conditions like rain, snow, sleet, hail, mud and steep hills. I am sure there are more scenarios but so far, rim brakes are looking decidedly unsafe and we haven't thrown in a bicycle trailer loaded with 170 pounds of touring gear.