I just got my girls, so beside personality, I can't tell.
But by personality, one is more 'prissy', more ladylike than the other. She's very dainty in the way she moves her head, walks, eats, etc. She's nowhere near as messy, and she also doesn't have as much of an attitude as the other.

Unfortunately, they don't really have names yet.
I call the prissy one Miss Priss, and as much as everybody doesn't like it, it may end up sticking.

I can tell mine apart because one has a thicker stripe on her head than the other one. Also one has a kink in her tail while the other one is completely straight.

Luna has a thicker back stripe than Aurora and Aurora has pale eyebrows (: At first I was terrified that I wouldn't be able to tell them apart physically (they have very different personalities at least!) but now it's as clear as day for me haha