100-300 or 75-300?

Has you or anyone else actually tried to systematically measure the difference in AF speed between the 75-300 and the 100-300? If so, could you please link to or describe the methods and results.

In view of the many subjective impressions I have read about the AF speed of the 20/1.7 versus how it actually does when tested, I am more than a little wary about taking user impressions about AF speed at face value.

I have the 100-300 but haven't had a chance to play with the 75-300. All I can say is that the 100-300 is very fast on the E-M5 when refocusing on a target at roughly the same distance as the previous one and certainly not irritatingly slow when moving between two targets at significantly different distance.

This is in good light and an AF target such that there will be no hunting. But both lenses need good light in the first place (unless you are shooting from a tripod with a static subject in which case AF performance doesn't matter) and I am sure both lenses are slow when they start hunting (which you should therefore do your best to avoid by choosing a good target and let go of the shutter button immediately when the lens starts hunting rather than wait for it to finish/give up).