I find that the only benefit of pull pull is in a plane where you would normally put servos in the tail. It will allow you to put the servos near the CG to better balance the plane.

Flexing of the pushrod will not happen with the proper rod. Your local sporting goods store will have arrow shafts which make excellent pushrods. If you perfer to spend a little more money, go to central hobbies and get there CF pushrods.