I like both (generally), but I'm more likely to own a cat that a dog. Dogs take a lot of time and effort, they're very demanding, needing to be walked and played with all the time. Cats are more or less independent. I'm not saying to ignore the poor thing, but they tend to be content to crawl into your lap and accept a simple petting or even just to fall asleep on you, where as a dog will watch to play fetch or something and they (typically) are not trained to go in a litter box so you have to stop what your doing to walk them.