Well, actually, this is hard to tell.
Per the conditions, it seems that Erza's PoF (and Makarov's spirit/power) has to be accounted for, which automatically tips the scale in her favor. She also has the DS enchanted sword and is at full power in this battle, unlike her fake condition during Irene's match. At the same time, Erza only has to slash Acnologia out of dragon form to win..
On the other hand, this is Acnologia we're talking about here. He has feats, portrayal, and hype all on his side. But there's one condition that may stop me from not choosing him as the victor..
And that's the 4th point.. Acnologia is a statue until Erza lays 5 hits of her choice.
Honestly speaking, now it's too close to call. The overall outcome in this match-up all depends on Erza's strategic moves.
I'm assuming she hits the 5 most critical areas, which would be her only chance of canceling out Acnologia's dragon form:
1. No doubt, her first two hits would have to be going for both Acnologia's eyes. That would immediately use up 2/5 hits. Not only will this blind Acnologia when he gets to move again, but the sheer pain may cancel out Acnologia's dragon form, thus giving Erza the instant win, which is what she needs.
This is kinda hax, cuz Erza can technically just not use the remaining 3 hits and stand there, waiting for Acnologia's blood to completely drain out. But I'm gonna assume this is not the case, only because that would be a cheap move.
2. If Acnologia still hasn't lost yet, then that means her chances of winning are pretty slim. She has the option to use the remaining 3 slashes on his Acnologia's neck area, but it could honestly be anywhere at this point. I would go for the neck area myself because it seems to be the most vulnerable part and probably the most painful too if you want to cause Acnologia to revert back to his human form.
Considering these conditions, there's no way I can vote for Acnologia, to be fair. I'm not gonna try to guess his power right now. At the same time, everybody knows I hold Acnologia to the highest regards. And I'm not willing to give Erza the win here either. Only time will tell if the victor of this battle is indeed Acnologia or Erza.
As a result, I deem this battle "Too close to call", as the poll offers.
Rating of this match: 5/5 for the in-depth points of the conditions.