Ok i had a hard time deciding on what to choose, some people choose cats, some people choose dogs. But i chose dogs because you can take them for a walk, give commands (sit, shake, roll over, etc), and they'll clean your face right off becuase you have one smear of sauce on you cheek.
Both, depending on the situation you need to live with them in. Dogs are more demanding than cats, on the other hand cats aren't as snuggly... Not all of them, anyway.