User blog comment:SethHeartphilia/Whos stronger Erza or Mirajane/@comment-189.79.216.47-20121007214547/@comment-4933386-20121008115844

Why are you thinking Yousei No Yoroi so strong?? Mashima barely showed much about that armor and it just stated by Knightwalker that it's the strongest... but still, not much was shown.

plus, as you said 3 months and she can take-over into her strongest one. But you don't know what does she mean by "strongest", I mean, what proves that it's the strongest??

If Erza doesn't have her Second Origin released, and Erza train exactly the same amount of days as Mirajane, Who would win?? What can Erza get out of that three months?? Or what if Mirajane got her second-origin released( if possible) as well, what would you say??

Like Seth said, Mirajane's magic was reduced due to her fight with Elfman and Evergreen. and Lisanna was held as hostage. If none of that happened, She probably has quite high chance of winning.