Hard choice, i've had both for my whole life, at the moment i have 2 cats.
People saying that they arent affectionate or loyal are wrong, my 2 cats are very loving and loyal and very entertaining too, to the point where they become annoying wanting to play and chase and fuck about at all hours of the day and night.
Dogs are good, but they need to be constantly walked for miles each day(if you dont then its just fucking cruel, people definately shouldnt have dogs that they cant take out for PROPER walks every single day). you have to clean up dog shit after them, they fucking stink. And they're a bit like kids, your own are ok and you love them to bits, but others peoples just fucking annoy you. I hate going to my mates house cos the dog if fucking hyper and farts the place out and wont sit still for a minute, i have to pretend to be allergic to it for them to get it out for a few minutes. Treat it like a fucking baby. You dont get this problem with cats.
But when i go on holiday (in the UK) or for days out etc i really really miss having a dog. I love border collies and would get another one tmw if i had the room and time to look after it.
Currently for me, cats egde it but only cos they fit into my lifestyle. If i lived in the countryside somewhere no doubt i would have a few dogs as well as the cats
ps "studies" show that more intelligent people opt for cats.