I agree with you, as I said that Kata has the best CoO portrayal in the series.
But that being said, we already saw most if not all of Kata's arsenal. While Mihawk is still a big mystery, even more than Big Mom, Kaido and what not since his prowess is not at all potrayed despite being introduced more than 20 years ago.
And since then, his portrayal is nothing but grandiose. One of the three known World Strongest title holders. "Equal to Shanks". Presumbly strongest Warlord. And most importantly Zoro's end goal.
I included the Shichibukai thing because it's one of the most important factor in the story. I can even go so far as calling it one of the main triggers of the story. This system is what makes One Piece as long as it is. Yes it sounds farfetched but stay with me.
As we all know, Oda first intended to end One Piece in 5 years with Luffy goes out to the sea and then goes on challenging the Emperors. This is a fact despite it being scrapped. Why? Because with Mihawk he introduced the Warlord System. Out of the 7 og Warlords, 3 of them are main villains for 3 different Saga (Crocodile, Moria, Dofflamingo). One of them is a great ally (Hancock). One of them is currently a crew member (Jinbei). One of them is the savior of the crew and plot moving device (Kuma), yes you heard me right.
And among those important people, Oda chose Mihawk to represent this concept. Yes so far, Mihawk hasn't played any role as important as his peers but you can't deny that Oda planned Mihawk to be someone really significant. So his fans have the right to hype him up or put their faith that he'd be stronger than a High End tier at their own field in my opinion.
Truth to be told I voted Mihawk's CoO more advanced too. But I do admit that Kata is better at it for now, because we simply haven't seen Mihawk do anything. Will take my "L" if it turns out differently than what I thought.