I guess it differs between people, what is easier to grasp :) . Pressure of air makes a real physical force (actually, pressure is defined as that total force divided by area). At the same time deflection downward, which implies an upward force, is correct but doesn't show the mechanism how actually that implied force is born. It is born out of the difference of pressure between top of the screwdriver and the bottom - at the bottom you have more or less undisturbed ambient pressure, at the top the flow reduces the pressure.

What was interesting to me is Ben's experiment with long enough cone which failed to get lift. Shouldn't be so, I think. The problem could be that his air jet is relatively narrow - so with a long cone, which makes an angle with the stream not the whole cone gets flown over, and not the whole area is under the reduced pressure. It would be very interesting to see if a wider air jet would still fail to lift the long tapered cone.