I guess the question is then which phenomena produces more thrust, partial vacuum or accelerating air?
The propellers will always try to go forward whether they are located in front or behind.
If they are located in front, they will pull the plane and when located behind, they will push the plane.
While there is a drop in pressure directly ahead of a propeller, I think it's more illuminating to think of a propeller as a device which accelerates air. Air is accelerated through the propeller, and since air has mass and F = ma, there's your thrust force. So it doesn't matter if the prop is in front or back, as long as air can flow through the prop and be accelerated backwards in order to propel the airplane forwards.
The same way you can push a cart, or pull it. You're still supplying motive force, just from the opposite end of the vehicle.
They are the same props, just driven from the other side.
The same way – duh ! !