As someone speaking in the present with all three out...Mifuyu is a damn good Dark Breaker, and while Fuka is too, Mifuyu feeds into herself in such a way that makes her superior depending on the situation, especially if you need someone able to deliver an ailment (though Fuka is better if the goal is mowing down enemies, as Mifuyu is a single target unit).

Also, Mifuyu isn't exclusive. So this comic makes me chuckle a lot at the irony.