@EmperorKinyagi
Katakuri clearly has a more advanced level of hardening
There a 3 levels of armament
- Basic self coverage
- More advanced version that lets you emit it outside of your body
- The most advanced version that lets internally bypass things with it
Each of them you can further strengthen your power/skill with it by further mastering it through hardening
Katakuri, Jinbe, and even Vergo and pica have shown a higher mastery than most when it comes to the first step
Skills like full body hardening, a tougher version of hardening in things like shark skin and diced mochi, as with katakuri being able to perfectly infuse it with his devil fruit body
Luffy has all 3 versions but had room to grow in each