I've heard the Nigerian Dwarf has the best tasting milk, but the larger breeds produce more milk, and are better for meat. It's really important to meet your goats and if possible, their parents before getting them. Behavioral problems are supposedly learned/inherited. I've also heard that there are some male goats that aren't as gross as others in terms of smell and habits. I've also seen that in dairy cows. Some seem to be always covered in poop because they like to lay down where they poop and what-not and some are very clean because they don't do that (this is comparing animals that have enough space to have these options).