I'm truly disappointed that many seem to overlook the character development that Mashima has shown with Erza and Laxus. Laxus went from the cocky, arrogant jerk with a chip on his shoulder who prioritised power over all else and desires to be acknowledged as the strongest. To a much kinder, and humble man. It was explained to us that Kyria's hypnosis blade was ineffective on him was due to the fact that Laxus regards himself as weak. When we, the readers and fanbase, know full well that couldn't be any further from the truth. It would thus be best to take what Laxus says about himself with a pinch of salt. Erza, on the other hand, succumbed to Kyria's hypnosis blade. It was also pointed out that Erza's artificial eye was what allowed her to reduce the duration of the effect of the spell by half the time. Otherwise she would be vulnerable under its effect for significantly longer.
During their fight, the multiple panels that showed us Erza's internal monologue as she struggle to come to terms how Laxus is constantly overwhelming her is enough evidence that she did not have a good grip with reality to begin with. In contrast, Laxus was never in disbelief over Erza's powers. When Erza busted out the Benizakura blade and eventually the twin swords, Laxus was intrigued but you could tell he was thinking 'Nice . . that's Erza for you'. He even asked Erza if she had any other attacks up her sleeve before she KO and didn't look surprise if she does. He rated Erza extremely highly and fought with the mindset that she is at least as strong as him. He valued her dearly as a comrade, as he was pissed when he found out somebody inflicted those serious wounds on her. He remarked out loud that he will settle the score with that assailant not knowing it was him. This was a far cry from the Laxus who mocked and downplayed Erza during the BoFT arc, while insulting her face being ugly when she was struck down by him.
In contrast, Erza fought with initial mindset that she could handle and defeat Laxus without having to go all out. She was in utter disbelief when the lightning empress armour was destroyed, her attacks rendered useless on him, getting sent flying across the cathedral by Laxus' attacks. She then stopped holding back and was eventually able to fight on an even ground with Laxus. The fight with Laxus taught her a lesson and at the end of it, she recognises that her thinking was erroneous and she is actually weaker than Laxus. For Erza to eat the humble pie and do a 180 turn on her stance is a remarkable change for her. Erza then fainted. Laxus took a seat on the ground before giving Erza her fair dues. That was in character with his portrayal. Then he faints too. Despite fainting later, Laxus woke up much quicker and carried Erza on his back whilst fighting against the horde of Wolfen's duplications. When Erza woke up much later, she could barely move without hurting due to her injuries. Let's not forget Laxus fighting Kyria beforehand too. Otherwise, he likely will not even faint at all.