You sleep more or less all day, only getting up to eat. You get taken out for walks to burn off all that energy and then you go home and go back to sleep. Your every need is taken care of. Free bed & board. You never need to work and you’re never in debt. You never owe anything to anyone. People will think you’re cute even when you don’t try to be. You’ll never have any complicated relationships or be stalked by any crazy people. You can’t talk, so you never have any arguments. Unconditional love from at least one person is a distinct possibility. However, even at best you’ll probably only live 15 years.
Taking all that into account, I hope I come back as a dog.