Why Oda chose to do that. Its pretty simple. Zoro has
always shown the ability to dodge and block his opponents pre time skip. And as a Swordman he also showed the ability of Ryou in his fight with Mr.1.
So what Oda chose for Zoro is only Natural for him to focus on the ability to cut/damage/hurt offensive/defensive while also trains his impressive dodging ability with CoO. And lastly
Zoro prefers not to act on emotion and that plays a huge part on how Taugh/Hard his CoA is since he is always confident that he won't falter no matter what
"ice cold steel".
As for Sanji its a bit different.
Sanji is a very observant person "aside from his peeking ofc" and his pre time skip fights showed to us that
he prefers to pinpoint/analyzing his opponent weakness and strength to take advantage of that. Or Straight up tricking his opponent after getting to know them for a bit.
So its only Natural for Sanji to be adept at CoO since its suit him best.
Also Sanji's character is all personality/emotion/compassion and that plays a huge part on
how easily he can sense people intentions and emotions "especially females" that alone makes him a better Observation user than Luffy
even if Luffy can use FS Sanji did show the ability to see more but not to the level of Luffy/Kaido/Katakuri.
Lastly his CoA is affected by his emotions and if you do not believe that go back and read his interaction with Black Maria and Remember what
Rayleigh told Luffy "Having no doubt is Power" and since Sanji is more human than Zoro it is why he falters alot and stumbles into doubts and frustrations easily.
Remember Sanji vs Queen? his ultimate Choice of being a
Weapon or a Human? That should summarize everything for you.
Great Post
