By the way, the trick on keeping out range cattle isn't the cattle, but rather the calves. If her calf can get through your fence, there's nothing you can do that will keep the cow out. Keep her calf out, and she'll not try to come through your fence because that would involve leaving her calf behind. Goats are a powerful technology, and power always cuts both ways. The same fire that will heat your house can just as easily burn it to the ground.
Goats are the same way.
On the other hand, goats can be hand milked, while for cows you really do need a milking machine. Since we do occassionly work with cows, we have a milking machine, but unless we have a cow, or are milking more than a dozen goats, the machine sits on the shelf. It's easier to hand milk half a dozen goats than to mess with setting up and cleaning the machine. Goats are very cool individuals. Left to their own devices, predators would have kept goat numbers down to the point where desertification wouldn't have happened.