Jeff Cooper used to say something like interesting things begin to happen to bullets at 2200 feet per second, roughly twice the speed of sound. Everyone knows that a bullet will penetrate a ping-pong paddle while a ping-pong ball will bounce off.
But imagine a ping-pong that breaks the sound barrier.
Check out this GIF and video on the Blaze. Seriously, click on over, the video is even better.
They tried to tell us that speed kills.
The lesson here is that velocity adds a lot to the equation -- velocity is squared in calculating energy.
For a bullet weighing 100 grains at 1000 fps -- 100/100 *1000/100*1000/100*2.22 or 222 foot-pounds. Double the velocity to 2000 fps and you get four times the energy -- 888 ft-lbs, whereas doubling the mass just doubles the energy to 444.
You could get a somewhat similar effect from a more solid, heavier ball at lower velocity, though I'm not sure if it would penetrate as prettily. The mass would tend to get imparted to the paddle slower, still resulting in it snapping off at the handle, but the blade would have time to start moving away from the impact. You certainly won't get the cool disintegration effect.