uh, assuming same cross section the wiffle ball and the baseball would fall at the same rate, and hit the ground simultaneously if dropped from a high building. From Wiki:

"In physics, gravitational acceleration is the acceleration of an object caused by the force of gravity from another object. In the absence of any other forces, any object will accelerate in a gravitational field at the same rate, regardless of the mass of the object. On the surface of the Earth, all objects fall with an acceleration of somewhere between 9.78 and 9.82 m/s"