The biggest difference between milk produced by human women and cows is that women's milk is designed for infants, while cow's milk is designed for calves. From a nutritional standpoint, human milk is starkly different from cow's or goat's milk.
Human milk, designed for human infants, has much less protein, calcium, and sodium than cow's milk. Cow's milk, which is meant for calves, has a much higher concentration of these nutrients, along with having less mono and polyunsaturated fats, carbohydrates, folate, and vitamin C.
One of the most important key ingredients that is lacking in cow's milk is lactose. Lactose contains galactose, a kind of sugar that helps the infant mind to develop properly. While there is some lactose in cow's milk, it's not nearly enough to promote the healthy development of human infants.
Cow's milk also contains a dangerous amount of protein, more than three times what's found in human milk. This high protein content is so dangerous because excess proteins can lead to changes in an infant's blood/alkali balance, which means an increased risk for infections and a weakened immune system throughout their lives.
While these levels of certain nutrients are dangerous for infants, in fully developed adults, they are insignificant.