It seems only logical that (a) growing plants to eat them is more efficient than (b) bringing an animal into existence, feeding the animal with said plants and

It seems only logical that (a) growing plants to eat them is more efficient than (b) bringing an animal into existence, feeding the animal with said plants and then eating the animal. So (b) is more polluting and more cruel than (a). It might be time to wonder if it is worth it.