In a vacuum:

* They fall at the same rate. In a vacuum, the only force acting on an object is gravity. Gravity accelerates all objects at the same rate regardless of their mass or shape (ignoring air resistance). So a frozen tennis ball and a regular tennis ball would plummet at the same speed.

In the real world (with air):

* The regular tennis ball falls slower. Here's why:

* Air resistance: Air resistance is a force that opposes motion through the air. It depends on factors like the object's shape, size, and speed.

* Shape and surface: A regular tennis ball is designed to have a fuzzy surface and a slightly oval shape that creates more air resistance. This slows it down.

* Frozen tennis ball: The frozen tennis ball might have a smoother surface (depending on how frozen it is), and its shape might be slightly altered due to the freezing process. This means it will encounter less air resistance and fall slightly faster.

The difference is likely to be very small. The effect of air resistance on a tennis ball, even a frozen one, is relatively minor compared to its weight.

In conclusion: While the regular tennis ball will fall slightly slower than the frozen one due to air resistance, the difference is likely to be very small.