I'll elaborate, but as an introduction: one is that aCoO can also be deactivated, and the other is that Katakuri isn't in the same physical tier as King. If they were exactly equals, Katakuri's skills would indeed hardcounter King, but as we know, people who's behind in physical power won't just win by "superior hax" in this series (more on that later). An example of that would be Kaido and Law, who has a lot more versatility and broken superpowers than the former, but lower attack power and durability.
I always see arguments about "what would it take to make King go speed mode", because he's objectively broken and invincible while in defense mode. However, almost the same is true for Katakuri: he's close to invincible using his advanced CoO, but that is also a mode of sorts that can be turned off, in his case unwillingly, either by being distracted or by the fight truly being too dragged out.
So what should be compared is, what happens when King goes out of his invincible mode, and what happens when Katakuri goes out of his invincible mode?
King - Speed Mode
- Still keeps all of his fire and magma-based arsenal, including huge AoE.
- Becomes fast enough to disappear from Zoro's eyesight without using his DF, which should make him arguably faster in hybrid form.
- Still has attack power strong enough to send Zoro flying despite blocking his swing. Can also parry normal CoC imbued attacks with his sword.
- Is still so physically resistant that he took minor damage from two direct CoC imbued hits (he was devastated by KoH so yes, he goes down with a single CoC imbued ougi, but we know how devastating every little CoC imbued punch is supposed to be). Once again, this was without using his ancient zoan DF.
Katakuri can use his CoO to keep up with his speed, but, strength-wise, Katakuri is below advancedCoA level of attacks and King (speed mode without his DF) can endure normal CoC-imbued attacks without going hybrid. This means Katakuri's normal attacks on speed mode King wouldn't be too different from Zoro vs Mr.1.
Katakuri does have the advantage of, by seeing the future, known the exact timing in which King's flames are going to disappear, but CoO can also be obscured through AoE (if King had enough IQ so I guess not).
King may be possibly turned into a big punching bag if he goes speed mode, but Katakuri's progress to taking him down would be more than slow and King wouldn't just sit still and let him launch every attack freely either, especially considering that, unlike with Luffy, Katakuri can't freely clash attacks with King throughout the fight. Why is that? Because King can clash attacks with CoC-imbuement and send post-rooftop Zoro flying backwards against a mountain after clashing attacks. Katakuri started overpowering WCI Luffy but Luffy managed to match his attacks one by one by the end of it, which makes Katakuri be possibly a full tier behind King in pure physical strength. It would take a long time for Katakuri to score a win by countering speed mode King.
Katakuri - aCoO turned off
- Keeps his big versatility.
- Keeps his speed (that was not on the level of Snakeman without his aCoO, meaning his attack speed is not an outlier stat).
- Loses his way of dodging attacks.
Just like he took some hits from Snakeman as soon as his aCoO waned, if he takes "some hits" from King, which is likely if King goes speed mode, it's GG immediately. As explained in the recent paragraph King's attack power is above Katakuri's own attack power, but even more so above Katakuri's durability, which gets bypassed by WCI's Luffy before he even had aCoA.
Both Haxes on
Even with both their haxes activated, King would spend zero effort taking attacks, like we see the Seraphims do now, while Katakuri would spend an active effort dodging big-ass AoE and quick-rate ranged attacks that can probably OHK him and that he can't just keep blocking like Luffy's. I won't argue that Katakuri simply slips up and fails a dodge, but there's still this to consider:
- aCoO requires full concentration. Said attacks, and the danger behind them (which Luffy's lacked) puts pressure, meaning Katakuri probably wouldn't be that chill as we saw then for long.
- Katakuri's "logia invulnerability" works by deforming his body to dodge by deforming his body around attacks. He can't do that around mountain-sized explosions and magma dragons.
Meaning King can take Katakuri down while both their haxes are active, but not the other way around.
This all is why I think King would beat Katakuri unless Oda had a narrative reason for the later to win against his odds.
And, just to be clear: I'm not saying Katakuri can never beat King, just that the scenario is a lot more unlikely to me, but this is the series in which Law and Kid beat Big Mom after all so what am I even doing giving it this much thought.