I love my nubians for milking, but I also love my nubian crosses and I had a wonderful milking pygmy at one time. So, how's that for a decisive answer, lol!
Nubians give lots of good milk. I have three does and they vary in the amounts they give. I had one who as a first freshener gave almost a gallon a day. Another first freshener about 3 qts a day and the third first freshener, barely a half-gallon.
I've had one doe freshen a second time with triplets and at the peak fo her lactation she could give over 5 quarts a day! But, I rarely milked her - jsut left her to raise her babies. Her babies are nearly 5 months old now and I've weaned the buck kid and left the two doelings on her so that I can lock her up occasionally at night and milk her the next morning. She still gives 1/2 gallon per milking and that's 5 months into her lactation. I love that doe!
I've also got two Kinder kids (1/2 Nubian and 1/2 pygmy) They are good milkers and their milk is delicious! I'm milking one who has dried up on one side and even from 1/2 an udder she gives nearly a half gallon a day. Her mother is my highest producing Nubian. The other Kinder gives bout the same amount - but from both sides of her udder, lol. She's a smaller goat - more dairy in appearance with a beautiful bag. I think she'll top that amount on her next freshening.
I had an exceptional pygmy that gave 1/2 gallon a day also-but unfortunately I lost her.
Nigerian dwarves are great little milkers also, even though I have no experience with them at all. I like a heavier goat that can also serve as a meat goat - so I don't really think ND's are for me.
Good luck with whatever you end up with! Oh, and personality makes a big difference! I just couldn't fight one continually to milk - my nubian and nubian crosses are wonderful on the stand. Maybe from generation after generation of being milked - or maybe just cuz they're hogs and will stand for milking as long as there is feed in front of them, lol!