It's best for baby. Breastmilk has antibodies in it from the mother that pass to the baby and help protect him against illness and allergies. Breastmilk is easily digested. Mothers don't have to worry about their babies being constipated or thirsty, because babies get an adequate amount of water from breastmilk. Sucking at the breast helps with good oral development.
Breastfed babies have fewer speech impediments.
Breastfed babies have good cheekbone development and jaw alignment. Consequently, there is less chance of needing braces and other orthodontial work. By the time the next feeding arrives, the mother's entire immune system is working to provide immunities. If the mother is exposed to any bacteria or viruses, her body will be making antibodies against them and these will be in her milk. Research shows your child's immune system will not be fully mature for many years.