Pictures were taken of a 4500 RPM grinding wheel to compare the flash speed for different flashes and different power settings (when possible). Also pictures were taken with a fixed light at fast shutter speeds.
The results; The 1/16 power settings on the Vivitar 285 HV and the Nikon SB24 were best with the 30+ year old Vivitar 215 not too bad. The power of the Vivitar 215 is about equal to the Vivitar 285 at 1/4 power. All of these were much better then the 1/8000 second shutter speed. I did not test my Canon flash because I have no way to remotely fire them but I would guess that low power settings would be the same as the SB24 and 285 HV. The Alien Bees were not so good at any power rating but they did seem to be a little better at high power then low power. That is not what they say it should be but it may have to do with the shape of the power/light curve with the higher power being more peaked even thought the over all time is longer.

Also interesting to see the 1/8000 shutter speed distortion due to the way the shutter slot passes over the sensor. The blue bar on the wheel is straight but came out very distorted with the high speed shutter.

My next question, Is there any delay in triggering if I use Pocket Wizards to trigger multiple flashes?

A few motion stopping flash pics are at the end of the gallery.