User blog comment:SethHeartphilia/Whos stronger Erza or Mirajane/@comment-3422455-20121008205849

In terms of power Mira would crush Erza and make her her bitch. In terms of overall stamina/endurance Erza would crush Mira. Erza will have to use her Adamantine, Armadura Fairy, or Purgatory armor against Sitri because if not Mira will rip her arms off.

Still, Erza would win.

http://forums.mangafox.me/threads/377484-Mirajane-vs-Erza-(Serious-Battle)/page9

That is my opinion on how the battle would go. Don't judge me. Mira is my favorite character FYI too.