I like cats and dogs, and have always had both for most of my life. Now, I am married to a person who does not like cats, so I don't have one anymore, and just have my two little dogs.
I think that both make excellent pets; although it depends what you want from a pet, to decide which is most appropriate as a pet for each person. Dogs are usually extremely attached to their owners, and will often cry all day, or worse, tear up the house when they are left alone for hours while the owner is away at work. Cats do much better at this, and don't mind being left alone all day.
However, if you spend a lot of time with your dog, and play fetch, or just go to the beach for a happy run together; then a dog is a much better choice than a cat would be. Even though a cat can be taught to walk along on a leash, most of them aren't trained for that; and a dog loves to go for walks with you.