My understanding is that the MOAR ke, the more potential for injury and the greater the braking distance...
Having a low vehicle means that injuries tend to be less, or to more easily fixed parts of the body, which favours the lower and usually lighter cars, as well as the reduction in kinetic energy.
The kinetic energy makes less difference when there is loads of it. A car isn't slowed much when it hits a pedestrian, so having more energy makes little difference. The height is the big deal, as it alters how fast energy is transferred to the pedestrian, so what force is applied.
Braking distance isn't much affected by the car mass, as the more mass, the more weight so more friction is available, given the all post 2004 cars have ABS, so can maximise the friction on all the wheels. Braking distance goes up as the square of speed, so in that way the kinetic energy makes a big difference.