You can train a dog to sit, roll over, go to the corner, etc. It depends on you for basically everything, and will be your best friend for life.
A cat can't really be trained. It does what it does as the easiest method to amusement, food or sleep. It doesn't admit to depending on you and if you stop feeding it, it 'WILL' find a new home. If it needs (more likely wants) something, it will come to you rather demanding. You are it's staff and it is the boss.
When a cat curls up to you, don't think it's doing that because it wants to be near you. You are in fact a warm thing to keep it warm while it sleeps. If it jumps on your lap it's because it wants a relaxation massage and will purr to let you know your doing it right.
A dog is faithful to a person. Your dog will lay there and starve to death with you.
A cat is faithful to the food dish. If you can't keep it filled, it will find better provider.
I really like my cats (singular at the moment). I never have to take it for walks, and I can leave it for days as long as I leave enough food and water.......and an extra litter box.