The answer to the question depends on what measure of efficiency you are looking for. In terms of stability, a sphere is less efficient since it can roll away!
There Isn't a shape bigger than the Icosahedron.
A dodecahedron
The size comparison between an icosahedron and a cube depends on their specific dimensions, such as edge lengths or volumes. An icosahedron has a more complex shape with 20 triangular faces, while a cube has 6 square faces. Generally, for equal edge lengths, the cube will have a larger volume than the icosahedron. However, without defined dimensions, it's not possible to say definitively which is "bigger."
A nonagon (9 sides) for example.
Icosahedron can be bigger
It has flat sides to balance on, a sphere just rolls around.
There are several but there is one that comes to mind that has 20 congruent triangular faces called an icosahedron.
A sphere.
Yes. Bird lungs are more efficient than mammal lungs.
Apples are more efficient than coffee in this case.
Gas central heating is more efficient than electric.Open cast mining can be more efficient than deep mines.
earth