Wetware is unbelievably, ridiculously efficient compared to anything we can make out of silicon and metal. Our most complex artificial neural networks, endless arrays of theoretical neuron-like structures, are much smaller, less complicated, slower, and less energy-efficient than the actual neurons in a brain. Of course, we can make computers as large and energy-consuming as we want, but this limits their potential to escape to the web and doesn't address the speed issue.