I have to disagree with the other Moderators, as there's great benefits to both pets. Birds are fantastic companions, many studies have shown that birds can mirror some of the human relationship that contribute to health. They're also very social animals and love social interactions. Cats have a great mind for learning while having helped many owners with reducing any signs of stress. This of course is if birds are real, which of course they're not. They're just robots!
Cats have relatively the same benefits, however, they're able to lower anxiety along with stress, a quick session of petting or playing will more than likely have your cat purr. The vibrations within that purr are known to have healing effects and will turn a bad day into a good one quickly. They also have a lower risk of heart malfunctions such as strokes or disease, due to a natural chemical cats tend to release when they're in a happy environment.
What I'm trying to say is, dogs are the best and my dog is the best boy ever.