People who choose dogs like to exert power over submissive, small-brained creatures, likely because they don't have any other form of power. Kind of like forum moderators.
I could go one further and protest the sacrifice of countless animals that go into dog and cat foods...
I would guess dogs, for some reason.
cats, no question. I have had, and will have, dogs as well. And horses. But for companionship around the place, cats. Dogs are OK, mind, but I dislike being uncritically worshiped -- something a cat will never do. Accept you, yes. Be actively fond of you, yes (even some of the barn cats!). But worship you, no. They know better...
In order of preference of the critters of various sizes I've kept and worked with -- cats, horses, dogs, cattle.
And ? Catwoman!!!