system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are round icecubes better or more efficient than square icecubes?
gpt
This is physics, not chemistry

Spherical ice "cubes" would melt more slowly since spheres have the lowest surface area per unit volume.  This might be considered efficient in the sense that the ice would last longer.  Also, the bigger the sphere, the more "efficient" it would be (thanks, square/cube law).

These "efficient" spheres are also more likely to allow your drink to warm above 0°C.  If you want your drink to be kept as cold as possible, even at the risk of the ice melting sooner, then you want the opposite of this sense of "efficient".  Small, crushed ice will be best; and the ice can never melt faster than needed to maintain 0°C, so smaller ice is not wasteful.