Well in the show they kinda seem to be perfect. Perfection is bullshit, even in a whimsical land like Equestria. I just like stories and things of Tia and Luna being imperfect just like anypony else. Other than that, I think Discord standing up for Chryssy is adorable.
I KNOW what you mean. I mean, seriously, why was there a HUGE debate over Derpy Hooves' eyes for? Her eyes made her unique and stand out from the rest of the "normal" eyed ponies.