You're asking about which is a better friend. That would be a dog, because well.. cat's are selfish.
If you'd ask about which is the better pet. I would say dog first because I just like dogs better, but cats are a lot easier (we have a cat and we can stay away from home for a night without a problem, can't do that with a dog) And she's attached as hell. (sleeps on the bed every night)
On the other hand.. we came home Sunday evening and the curtains (and everything that goes with it) were lying on the floor.. (first time ever so we're not worried...

)
(Oh and for 'the record' (aka my personal opinion), nothing smells worse than cat's breath, ever had a cat look at you while burping or something? Yeck) xD