My 70-300G ED VR does make me move back a couple of inches for minimum focus distance at 300 compared to 70. That said, I believe the distance from the front element to the subject is the same. Sensor to subject distance is different, I have to back up just a bit, and while I didn't measure, the difference is very close to the length change of the lens barrel. So in this case, I would say the minimum focus distance is different, measured from the sensor plane. Lens-to-subject, probably the same distance.