This is the only uninterrupted top tier fight in the entire series which actually had an outcome. The winner was Akainu. He then became FA while Kuzan lost a limb and became a YC after wandering for months.
Now, there's not much of a difference between them, for they are, relative. But no they're not equals. Equals would be Roger who didn't have a winner between him and Garp. We got a definitive winner and the only winner between an uninterrupted top tier fight in the series. They're relatives, not equals.
Akainu is stronger. That's all there is to it. Maybe it be by a strand of hair but he is stronger.
And I'm willing to wager that the gap between the two has increased since Kuzan's will probably got weaker after he left the marines and pointlessly wandered till he joined Blackbeard while Sakazuki got narrative buff by becoming FA and making the marines the strongest it was.
Akainu extreme diffs Aokiji every day of the month and no matter how long the fight takes, the winner will never change.