retrolefty:
No it wouldn't. The air resistance would be the same for a same size ping pong ball no matter what weight difference. Didn't Sir Isaac Newton demonstrate that weight is not a factor in a falling object?
I'm very surprised to see that from you retrolefty. Sir Isaac Newton's experiment only works when the effects of air resistance can be ignored. If you drop a feather and a cannon ball, the feather falls more slowly.
If the balls are being dropped through a pipe that is anywhere near the size of the balls then the aerodynamic blockage will cause a much higher drag than you'd seen in fresh air. This would have a much greater effect on very light balls such as a ping pong ball. You may also see mechanical drag if the balls start bouncing off the sides of the tube.