I'm fairly sure that my Racha is actually a cat shaped surveliance unit sent here by aliens because she is so strange, but she's also VERY friendly! In fact, I've found that most cats if properly socialized are wonderful companion animals. I like dogs, but am allergic and way too busy so I don't really know much about ther preferability as it were.
My ex-roommates had ferrets and it was AWFUL. They pooed everywhere, smelled horrible and dug up the furniture. Not to mention the constant noise.