Cats, no contest. At this point, I seriously hate dogs. Why you ask?
Pros (cats) - Cats for the most part do not require excessive amounts of attention. Yeah, they may rub on your legs or walk over you while sitting or lying down. But they are pretty much like, "Hey dude, what's up? Can you spare a scratch? Ah yes, thanks. Bye." Then they walk away and you're both content. They can also take care of themselves to some extent. They can handle their bathroom times on their own schedules without you having to constantly stay on top of things. Plop down some food and water and they'll make do for a while. The most you have to do is scoop sand from a box once every couple days. They can also catch little prey things like moths, mice, and other assorted things to eat if available. They usually have calm personalities and don't have to expend massive amounts of energy.
Cons (cats): Some cats can become destructive when sharpening claws. They don't have common sense for property value and can be annoying when scratching furniture or carpet. They also gag up those soggy bolus things with wet hair tangled in it, although with the right food they are limited and quick to clean up.
Dogs (pros): They will usually eat anything you give them and very quickly. This can be good for cleaning up messes that you're too lazy to clean, but they also eat things you don't want them to eat, like leather items, dropped medications, poisonous substances, and choke hazards. That said though, they aren't picky eaters for the most part and won't starve themselves to death until you buy something they like. Dogs can also defend property by acting aggressive towards intruders and alerting you with barking, giving them a loyal aspect. They can also be trained to obey little commands.
Dogs (cons): Christ, this is so long I have to make a list.
- They cannot attend to their own needs. You better stay on top of their bathroom habits or else they'll piss and crap all over the place. You can't have a dog if you spend long times away from home, such as for school and other events like traveling.
- If they don't get fed routinely, they cause destruction by eating expensive or dangerous things. And of those dogs that don't, they just starve.
- Dogs require massive amounts of attention. If you don't constantly expend your energy playing with them or taking them on walks, they create their own fun by destroying things, barking, and being a nuisance around the house.
- Dogs have no respect for personal space. If they want attention, they want it now. They'll just jump on you while acting obnoxious.
- Many dogs chase things and get themselves lost, hurt, killed, and/or get the owner in trouble with neighbors or animal control.
- If a dog decides to be aggressive, they are more formidable and generally cause more physical damage than a cat would. That being said, if a cat decides to be aggressive, you can walk away from it. A dog however may decide to follow/chase.