The extra contact (on the ME Super hot shoe) lets the flash unit set the camera's shutter to X-synch (1/125 sec) when it's fully powered. It might also enable firing control depending on the level of dedication that the flash unit supports. Firing control is where the shutter release is disabled until the flash's capacitor is charged, but my Metz's don't support that function so I can't confirm that ME Super offers it.
I can confirm that the ME super doesn't feature firing control. :-)
S
