Dogs, it turns out, have about twice the number of neurons in their cerebral cortexes than what cats have, which suggests they could be about twice as intelligent.

Making the dubious assumption that intelligence is directly proportional to number of neurons. Given the complexity of neuronal networks, I'd expect the relationship to be highly nonlinear.

Plus, number of connections probably matters more than number of neurons.

Having said that, doh, of course dogs are smarter.