I like both, but, if forced to choose, I'd go with a cat. Then again, I'm probably biased since my sister and I actually own one.
The kitty, Aria, just finished giving herself a bath and she's now sleeping a foot away from me as I type this.
Aria is a bundle of affection who follows us around and always wants to snuggle. If only one of us is home and we're behind a closed door, she sits outside of that door and waits for us to come out. Once the door opens, she does this sharp, excited meow and rushes over to rub against our legs (obviously, she seems to think that she hasn't scented us enough to mark us as her own). Aria also began playing fetch without us ever teaching her. Seriously, if we shoot a hairband across the room, she runs at it, bats it around once or twice, picks it up in her mouth, trots back with it, drops it at our feet, and looks up at us expectantly. She'll even start meowing and pawing if we don't pick it up.
When Aria sits in a windowsill, she tries to get our attention if she sees animals in our yard (especially birds, rabbits, and coyotes) and she won't make that predatory chirping noise at anything unless we put a hand on her. It's almost like she needs comfort to be brave; however, she treats strangers to our house like best friends. Aria needs no warming-up time when it comes to people she doesn't know - she gets as excited as any dog I've ever had in the past.
I like to think that our kitty is a perfect argument against the notion that cats only pretend to care when they want food.