Cats for the win.
Most dogs that look even remotely not ugly are big, except for a few exceptions. The small dogs that are not ugly are expensive.
Dogs tend to not live as long as (well taken care of) cats.
To play with a dog, most of the time you have to throw something, and when you want it to stop, it just keeps coming back. With cats, you could just attach some yarn to a ceiling fan, turn it on, and there ya go. You get to sit back and watch.
Although some think that cats cannot be trained to do things, this is not true. I have seen many cats that are trained to do tricks.
Furthermore, cats are generally more quiet, and sleep most of the day, where dogs tend do be loud and run around all day.
To be honest, I always liked dogs, but then I got a cat and I began to love them.
Cats all the way, no contest here.