If you want a LOT of milk, go with Saanans.
If you want a lot of milk and a LOT of butterfat (to make more cheese, yogurt, etc) go with Kinders. They're a new breed, based on Pygmy x Nubian, and are on the medium/small side, but they're very easy to handle, half the trouble of most other breeds, birth very easy, and not only do they come in some amazing spotted colors but they give up to 1 gallon a day, with their milk ranging to contain 6-10% butterfat. The average cow has a little over 3%; The average dairy goat has a little over 4%
Here's my own little starter herd of a few kids and a 4 year old doe who produces GORGEOUS babies and has the highest butterfat of the group. I've made a lot of cheese from her milk, and she's very sweet.
This herd also replaced my previous LaMancha goats. Honestly I found them to have far too little butterfat, not the best tasting milk, and they were the most troublesome, bratty goats I've ever known. . . .