Haven't seen anything from Irene since this thread was made that change my opinion.
August is faster, more durable and his performances were more consistent.
Jellal and CS couldn't touch him in their fight. Jellal with Meteor has some unholy speed, eclipsing DF Natsu in ToH and Acno. Cobra, Racer and Midnight all had very effective abilities. August ran rings around them. They could've fought for another zillion time, and August would still emerge unscathed.
This is the destruction Gildarts can do with a simple punch.
His basic spell has a 100% track record of KO-ing his opponents in one hit.
August took Gildarts' most powerful spell in his face from point blank range. It left him with a small cut and little bit of blood on his lips. That's a tiny, surface wound. August endured a broadsword impaled through his spine when he was taken by surprise from Brandish's attack, and quickly retaliated. Erza managed to cut apart Deus Sema, Irene's strongest spell. Erza was at her peak POF then, but she is also weaker than Gildarts. Erza probably has greater POF, but Gildarts is naturally stronger and more powerful by default, plus he had his POF when trying to protect Cana from August too. It is reasonable to think Deus Sema is unlikely to bring August down.
Irene in her dragon form has more physical strength than August, and she'd better relying on her claw swipe. However, I'm inclined to believe Melt was a DS spell. Even if it isn't, I find it hard to believe that August at his age does not have a DS spell in his arsenal.
I don't usually use portrayal, but I feel there is a good reason Mashima left August as the last one standing and he made the effort to recognise this.
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