> The authors find that being hit by a 1,000-pound heavier vehicle results in a 47 percent increase in the baseline probability of being killed in the accident
The linked article just looked at collisions that happened and compared danger by vehicle weight. If I had to guess, I would assume lighter vehicles generally have a shorter stopping distance and hit pedestrians less.
The vehicle stopping distances are generally close enough that the only things that will matter in a practical sense is the reaction time of the driver and the condition of the vehicles. From 60mph to 0 in a Toyota Camry is 122 feet, and an F150 is 129 feet. The age of your tires/brakes blow away that 7 feet of difference.