They scratch, they are pointless, you can't build up a relationship like you can with a dog, they cant be used for work-like purposes, they dont fetch stuff, they make me sneeze, you like them, they get hair everywhere, they kill birds and fish.
they kills mice too you know? at least with a cat you have less responceability e.g. no walks. im not sure i would have either a cat or a dog to be honest.