[_vk_]

Mostly the latter, I believe.

The human brain uses the incredible 20 Watts to achieve things that modern megawatt supercomputers aren't capable of.

[whitegrape]

I think the figure is closer to 100 W average across the day since the brain cannot exist in isolation of the body which needs ~2000 calories daily, but still, we're fairly efficient. We're built with advanced nanotechnology.