For me definitly cats. Dogs are to energetic for my lazy person and sometimes they annoyed me... (sorry for everyone who love the dogs). But i think that thats depent on what type of person you are.
If you are energetic, then definitly dogs, but if you are house rat then remember - with dog, you need to go out.
Dogs because they always want to play around, but i will not rlly have any pet for myself, there is a dog from the family so it doesn't get lonelly when nobody is around. cats do not care much to be alone for a longer time at least the ones i see friends and other persons i met owned.