In all seriousness though, August can and should triumph here. And here's why.
Skill - August has shown an unprecedented control over his ability. He learnt all moves instantaneously, just by bearing witness to them being performed, nullifies their effects on himself, and turn the volume up to eleven to hurl them back at his foes with greater intensity. The degree of mastery in his skill saw August delivered an emphatic asskicking to Jellal and Crime Sorciere despite the numerical handicap. He beat all of Crime Sorciere at their own game.
August flattened Gildarts by quickly counterattacking after completely reconstructing himself from Crash. From a technical standpoint, August has fired on all cylinders, and has an unblemished track record against all Caster magic he comes up against. Irene, on the other hand, did not display such a level of proficiency. She was, however, hoisted by her own petard when Wendy, who is vastly weaker and inexperienced, was capable of wrestling control of Irene's body with her own enchantment, and expelled Irene out of her body.
Speed - We should all be aware by now that Mashima seems adamant on portraying Jellal's top speed in Meteor as probably the highest amongst the mages. Though he wasn't able to hurt Acnologia, Jellal has shown to be able to outspeed Acnologia in some instances. To the point where he could generate sufficient velocity to push Acnologia towards the ravines of time up to a certain distance.
August, without breaking a sweat, literally and figuratively ran rings around Jellal. He dominated him, along with Crime Sorciere, who barely even touched him. Gildarts, who could anticipate August's attack, was not able to dodge with his reflexes.
The same Gildarts who has amazing agility and is deceptively swift.
Irene's speed pales in comparison. Erza and Wendy were able to land successive hits, and damaged her. Her best possible feat in her dragon form is probably the time she ascended to the sky in a single bound.
But it is ambiguous if she achieved so with natural flight. August should be faster as he had simply displayed greater consistency in this regard.
Mentality - Perhaps most crucially, why this fight should sway in August's favour is because of the attitude these two takes when it comes down to crunch time. August does not muck around and is far more decisive. When Mira was at their disposal, August finished her off in an instant to prevent any potential hindrance. In contrast, Irene intended to torture her for fun before killing her.
More often than not, Irene has a tendency to let her emotions get the better of her. She did suffer from a heavy amount of PIS during her fight with Erza and Wendy, but still she succumbed to her emotions after intially setting out to kill both Wendy and Erza. Even she herself was admittedly surprised at her own change of heart.
Yes, Ars Magia did jack all eventually. But it was foreshadowed beforehand by August himself, that he can only be 'defeated' by his own mother. And it did turn out to be the outcome, though not exactly the way we would have hoped. I don't think it is debatable that Irene is at least somewhat emotionally unstable, which leads to her judgement getting clouded.
I do feel they will break even in some aspects though. Irene broke all of Erza's bones, but August is definitely no slouch when it comes down to physical strength. Gildarts who could destroy huge landscape with a simple punch, without his magic.
And constantly besting Natsu in an exchange of strength.
The same Natsu who launched a guy with a towering physique into the skies and through the airship several hundred metres above the ground with a basic punch.
August was pinning an enraged Gildarts back for majority of their fight.
And while Irene's Master Enchantment in her dragon form was able to transcend skies and earth, August just by exerting his magical presence was effortlessly causing the earth and skies to crumble and disintegrate.
A full powered attack from Gildarts' strongest spell could only take August down a for a few seconds, but could not keep him down.
August is also a damn anomaly. A freak of nature. Considering who his parents were. Two magical prodigies, who shares the same curse from an actual deity, not the half-baked ones who roamed the earthland.
He was abandanoned by Precht, the same Precht who created Fairy Heart but did not know how to handle August. He also learnt about all of Zeref and Mavis relationship and history just because he can, despite not acknowledging them in person before. I don't think it is wise to apply conventional magical limitations to scale August and assume he cannot defeat Irene because the latter has a dragon form.
Irene is definitely not going down without giving August a tough fight though. She is extraordinarily powerful in her dragon capacity, but August phenomenal skill, intellect and competency will prove to be too much for her handle.
Ultimately, both August and Irene were characters who required the author to save the protagonists through contrived plot devices and engineering their own death because Mashima wrote himself into a corner. Here I am glad they are in the finals, even if I did not have the time to participate in the semis'. Either of them winning will be well deserved. May the best
more popular combatant wins.
