It totally depends on what you want to use a measure for. Just like neither height or volume alone will tell you what will fit in your car.

By any measure that puts energy used by the brain in the denominator, humans are probably dumber than ants. But that doesn't mean those measures are always accurate.

(For contemporary neural networks, you also have to distinguish training costs from inference costs.)

For inference that could be useful, but the energy is not for the model it is for at least the tuple of: model, model architecture and compilation, and hardware chosen.