I've had both and my answer is definitely cats. Dogs remain stupid their entire lives, they shit in the house, pretty much destroy everything, chew everything to bits. You need to constantly walk them, pet them, play with them, watch them, etc. It's more than a pet, its a full time job. You can't leave a dog at home by itself either.
Cats give you the same love you give them. Once you learn how to properly interact with a cat, it'll love you and you'll adore it. Some helpful tips:
Cats see staring at aggressive. Thats why they look away from you all the time, they're trying to say "hey man, im cool with you, dont worry". The less eye contact you give a cat the more it will like you and the more it will want to be around you. The mistake many people make it seeing a cat and instantly treating it like a 'dog' "hey buddy, c'mere buddy! *slaps hands together* c'mon, stupid cat!" you're litterally scaring the thing.
A cat is man's best friend, in my opinion, dog's are great at chasing escaped convicts and finding drugs. And shitting everywhere and basically being little monsters.
hoo, boy, here come the flames!