You mean energy-efficient, this would be neuron, or synapse-efficient.
So, my first response to your comment about the memory not being in the synapses was to agree with you. But I also agree with your respondent, so, hm.
Horsepower comparisons here are nuanced and fatally tricky!
The general point is valid though - for example, a computer is much more efficient at finding primes, or encrypting data, than humans.