Dog is essentially a servant. His feelings toward his master are comradely and his manner familiar; he enjoys the master's affection and regard. He will go to any length to please and protect his people. He can be taught any manner of service tasks and will go about them with enthusiasm. His aim is to please.
The cat is different. She serves no one, knowingly or willingly. Her one accomplishment -- the hunting of mice, rats and other rodents -- is self-taught. The man does not live who can claim to have trained a cat to perform a task for human benefit. There are no police cats, no watch cats, no sled cats. The cat does not even come when she's called, unless it suits her.
Dogs are dependent upon humans. They seek humans for companionship, play and care. They enjoy the role of being part of the “pack” and will go to great lengths to keep that position.
Cats are also quite self-sufficient. You never have to entertain them. This is not to say that they cannot be entertained or that they themselves are not entertaining. It is just that their errands are many and their schedules full. Cats prefer going it alone, depending upon their own wit to survive.
Whether you choose to share your home with a dog or a cat depends a great deal upon your own personality. If you seek to be in charge, you will come to blows with cat every time. She cannot be controlled. If companionship and undying loyalty are what you seek, a dog will fill the position willingly.
There are homes and people for both dog and cat—examine what you expect carefully and choose accordingly. Your home will be blessed with the presence of either.