If we go by manga continuities alone (and even this can get messy, as several articles by Antie could show), Minako knows more because she's come unto her power earlier. She therefore had more time to develop it, discover its hidden meanings, and converse with Artemis than the other senshi have. After all, Minako became Sailorvenus, or Sailor V as she shortened it to, at the age of 13, while all the other senshi were given their powers a year later.