Breastfeeding is all pro in my opinion. It is the perfect food created especially for babies, has all the nutrition they need for early life, has many ingredients that scientists can't reproduce or imitate, is the perfect temperature for baby, always ready when needed, safe and will not spoil, ultimately portable, doesn't require washing or boiling, etc. -- the only downside is mom has to be there. This issue can be dealt with though by using a breast pump.
Of course, babies will thrive and grown on formula. It fills a vital need for babies when breastfeeding is not available. Scientists continue to improve formula, but I doubt that it will ever measure up to "babies perfect food"--breast milk.