The four year old looks like a better goat, to my inexperienced eye. But to me that seems fairly expensive, unless she's papered? Not saying she's not a good investment, but I'd expect her to be registered, etc. If price were an issue, however, I'm sure the two year old would be a good household milker if that is your main purpose.
LaurenLewis, I always enjoy your Goat A or Goat B quizzes. They make me look and think!
Oh, goodie, Alpines. I love them. In the picture the 4 year old looks nicer but this is I think, but may not be, because she is set up nicer in the picture. The 2 year old looks nice but her legs are not set up as nice. The older doe has more capacity in body and udder but once again she is older and that is to be expected. The two year old is a FF so she has some catching up to do. I think that overall she is an equally nice doe as the 4 year old.
For either show or milk, get the 4 yr old. She is well put together, much better than the 2 yr. Not much I would change about her, as is, I would personally buy her and have her as part of my herd.
My 2 cents, do with it what you will.