I've always been a cat person, for most of the reasons already stated, but am allergic to them - highly allergic. There is one cat whom I have known who didn't make me sneeze into a frenzy.
Then, my mom got a Bichon Frise. He is small & portable - like a cat - but has a lot of the loving dog personality, too. I didn't want it to happen, but Buffy has his little paw prints all over my heart!
My brother & his wife have two very poorly trained Dobermans. At Christmas dinner, they put their heads on the table and drooled. If that wasn't enough, we had roast beef - you know how you cut several slices and fan them out, leaving the rest of the 4-5 pound roast intact? The one dog grabbed the big piece of meat and clamped his jaw on it! After wrestling it from the dog's mouth, my brother offered it back to my mom, who passed. Who wants it after it's been Dobified? blech. Anyhow, I've taken to calling them the Bumpkiss' dogs...
As to the original question, I think it's the personality & training of the cat or dog in question. Both improve your life considerably!
