I would wonder about dog vs other animals.
With dog you have to walk outside even if you have a garden, a dog needs a daily walk a bit further around.
Cat doesn’t need a walk, well it requires play time but I would say walking around the block should do more for person health than playing around with cat in-house.
I wonder if owning both a dog and a cat scales linearly, or if the combo is synergistic.
Well, there’s a physical aspect and socio-mental aspect. A dog probably would be better for the former, but cats aren’t as straightforward as dogs to please or understand and require increased ability to put onself in another’s shoes and view things from their standpoint. Cats are a lot like little furry people in terms of socialization.