Some people say the berry pickers damage the blueberry bushes. Other people say they do less damage than bears, and are therefore not harmful. No one seems to think they harm lowbush cranberry bushes. There is a village I know of that will allow anyone to come and pick blueberries in their area, but they won't allow anyone to use steel berrypickers. It will take time and careful observation and measuring to do the following experiment, but a good scientific answer is possible.
Experiment Find several patches of blueberries.
With flagging, divide the blueberry patches rougly in half. Harvest the berries on one side by hand, and the other side with a berry picker. I would probably go by weight. Record the weight, volume or number of berries from each section. Hand picked area 1356 grams of berries.