According to the Daily Beast, dog wins.
They are more intelligent than cats -- even if cats act like they're smarter.
I have to admit, I have mixed feelings about this.
On the whole, I think I'm probably more of a dog person than a cat person. (Although I'm allergic to both.)
I was bitten by a dog when I was a kid which pretty much soured me on dogs for my entire childhood. But, now that I'm less afraid (although not entirely cured) I like a dog's enthusiasm; I like their unqualified affection; I like the fact that a dog is accepting and loving.
Cats have way too much of a glib, what-have-you-done-for-me-lately sort of attitude.
Many years ago, Ron Rosenbaum made the argument that this was actually a case for feline superiority -- you have to earn your cat's love. The fact that a dog will love anyone who feeds him makes their love essentially worthless. (My favorite line in the piece is, "After 11 years, I'm still not sure if I have the love or respect of my cat Stumpy.")
It's an interesting point... but I'm not sure pet/human relationships really should center around such things. You didn't buy a cat so that you could woo this cat into loving you, did you? Don't you just want to come home to something that holds you in high regard? Who is grateful for the food and water you put out? Who is happy to see you?
I mean, how much work is Rosenbaum really proposing putting into this relationship?