http://www.breastfeeding.com/advocacy/advocacy_bfinpublic.html

In the United States today, there’s a new awareness of the serious problem of overnutrition and of the problems caused by overweight. Bottle-fed babies tend to be fatter than breastfed babies. One reason for this may stem from the fact that bottle-feeding mothers who see milk left in the bottle tend to encourage their babies to drain the last drop, while breastfeeding mothers usually assume that their babies know when they have had enough. When the baby stops suckling, the mother takes her off the breast.

Another way that nursing may discourage overfeeding lies in the difference between the high-protein milk produced at the beginning of a feeding (fore milk) and the high-fat milk produced at the end (hind milk). The richness of the hind milk may make the baby feel full and send a signal that mealtime is over.

If you search, you’ll discover many experts in parenting and breastfeeding state that tidbit of information.

You can force a bottle in a baby’s mouth and they will drink, it would be very difficult to do that with breastfeeding. There is also the measuring aspect, many with a bottle try to get the infant to finish the portion in the bottle, with breastfeeding unless you weigh the infant before hand and then after there is no way to measure how many ounces is consumed.