Generally I prefer cats, because I speak their language better, and they're not so much about trying to make me fit into their pack structure. Instead, I'm the momcat - the one who takes care of them, rather than having to continually force the dog-brain to stay in beta or lower mode.

Cats also deal with their own poo better than dogs do. I don't expect to have a roommate in future, but if I did, no, they couldn't bring a dog, while I have my cats already. Because the cats are already balanced and don't need to stress out.