I've had both all my life (along with lots of farm animals), and I love them both. But right now, we are a two-cat family. Punkin and Sabrina (both fall adoptions). I would enjoy a dog - they're simpler, and they just love love love, but we are in the city, in an apartment, and I would never do that to a dog. Not with my schedule!
My cats are friendly and loving and follow us everywhere... not annoyingly, but you get up to go pee and suddenly one or two just happen to be wandering into the bathroom. Verrrrrry casually.
They come when called, sleep with us at night, keep us company when we watch TV or study or are on the computer. They are as comfortable being held as they are just hanging out. ... they're pretty awesome. I love 'em.