I think props don't get much thrust from 'suck' as opposed to 'push'.

Props are like wings - the "upper" surface, i.e. the front
prop surface is critical to good performance. The pressure
differential between the front of the prop and the back is
what produces the force that moves the aircraft forward, and
most of that differential (when compared to static pressure)
is due to the lower-than-static pressure on the front/upper
surface of the prop/wing.
Todd Pattist

Actually, I think the current thinking is change of momentum in the downward
air direction. there was an extensive thead on this in the newsgroup.

Think about this, standing by a fan: you feel more force downstream, where the
air is moving in a fairly well defined column, rather than upstream, where in
fact the air is drawn in from all directions.