Dogs are certainly better at looking intelligent. I think dogs, being a more social animal, are more eager to please, and so are willing to be trained.

Cats can vary wildly. One of my cats seems dumb as a box of rocks and haven't even grasped the idea of object permanence. If she's tracking a laser, and I move it around a corner, she can't figure out where it went. She goes from intense staring and tracking to standing up and looking around, confused. When I bring the laser back around the corner, she's instantly back to squatting and tracking it.