Board Thread:Questions and Answers/@comment-25908228-20141222101442/@comment-1200981-20150925055437

As mentioned, Yuuki has the ability to react at speeds higher than Kirito and it's acknowledged by the author that without Excalibur's stat increase, he would legitimately lose against her. He even said that Dual Wielding wouldn't make a difference. As for Asuna and Kirito, both of them are stated and shown to be on similar levels in the series, with Asuna having greater attack speed while Kirito has superior reaction speed. Like Gsimenas said, it's hard to say which one of them is stronger.