I voted cats, I love 'em. Dogs are, as some people said, a little too social for me.
But then again my parent's have a tom cat, and we're always joking about how you could have bred a "dog-cat" with him. He needs a lot of attention and prefers to be in company.
The other cat, however, is just a very typical cat, very wild, proud and with an own mind, she's much more independent.
I'm afraid, though, that none of them is that intelligent. I still love them to bits, of course.
About this thing that cats are "sadistic":
Cats are carnivores that hunt their prey. Their instinct tells them that they need to hunt in order to stay alive, and that they are domesticated doesn't change anything about that.
The difference about a cat living in the wilderness and a cat that's a pet is simply that one cat usually is hungry and the other one is usually not.
So the pet cats are faced with the dilemma of not being hungry but still wanting to hunt. And furthermore they usually live in areas that make it difficult for them to catch anything at all.
So when they finally catch something, they're delighted to actually HAVE caught something, but they aren't hungry. So there's no need to kill it at once, and if they finally have a "toy" they want it to last. So they play with it.
A hungry cat that eats it's prey, ot a cat with plenty of prey to hunt will not play much, unless it's a female cat teaching her children.