Imagine a farm animal, like a steer, that only exists because it was bred and raised to be slaughtered for meat and leather. Is it better (by whatever definition of “better” you have) for it to have lived or to have never been born at all? Is it any worse to be killed and made into steaks and shoes than to die of old age diseases and become worm food?
Imagine a congenitally deaf and blind puppy? It can still enjoy life, but people who keep it wouldn’t have room for a healthy puppy they’d keep otherwise. What’s better, for the deaf and blind puppy to have a life, or for a healthy one? Or would those two lives be equivalently good, by whatever definition we use.