Answer:
the bowling ball
Step-by-step explanation:
potential energy is given to objects by forces or energies that are applied to these objects, but due to some boundaries or blocks the objects cannot react to and show this (therefore) potential energy.
yet, as soon as the blocks are removed, the potential energy will turn into actual energy.
in our case Earth's gravity is pulling on both balls giving them potential energy, as the shelf is blocking them from acting on it.
the bowling ball has the greater mass, which is also expressed by its higher weight. and that gives it the greater potential energy (expressed by e.g. the impact damage they would do when suddenly falling from the shelf).