It's very obvious that oda cares more about Sanji as a character this question feels like a set up
I don't think it's about who Oda cares about more. That's like saying oda gave sanji more deeply embedded issues =, therefore he cares about him more.
A character that lacks conviction, and has a bunch of other issues, which leads to things like mental breakdowns, trauma or whatever, and you watching them slowly climb out of that hole
Then you compare it to someone who already had supreme certainty in where they were headed, you're saying the former had better progression so oda cares more about that character.
You can even say Koby has had better progression than Zoro using this logic. So he cares about koby more i guess "HE WAS ON THE PANEL OF MAIN PLAYERS AFTER ALL, NOT ZORO"
Sanji is the one who's telling people to abandon their dreams, then sees something in luffy's dream and decides to follow him because he
sees in luffy a mirror of qualities that he's like to see reflected by himself. Which has culminated to this very chapter 1187, with becoming a king.
Then he goes and leaves the crew because he lacks conviction luffy is strong enough to get through the current state of events (what did I say about that mirror? in reality it's reflecting
his own belief in his powerlessness) , with big mom on WCI, then he needs to be told by luffy and
reminded of his self worth and why he joined the crew in the first place.
Then when he's over that hurdle, he has the hurdle of being carried by germa tech and his family bloodline who he hates, in wano, then he has to now solve his wavering conviction of being good enough to help luffy be the pirate king yet again, which is stopping him from unlocking conquerors.
Whereas Zoro already had his certainty from the promise he made to Kuina. This is why I say Zoro is the type of character who was going to achieve his dream anyway, meeting Luffy just sped up the process.
Zoro was in it for himself, but then he humbled himself because he found a purpose greater than just his own goal. Yet even then he did that because he had supreme confidence in Luffy, and wanted to live up to Luffy's trust, the only way to get strong enough to do that was to accept training from the very man he wants to defeat.
Zoro as his character archetype in a shounen is pretty much as good as it gets. You don't need deep embedded insecurities with Zoro, like you have with Sanji. If they both had that they'd be the same shounen character.
The real people who need development are the fans who religiously chose one side and now must die on that side. This is why I had to stop being a zoro-tard especially after that whole ZKK debacle.
Maturing is realising you can enjoy the narrative instead of being an upset loser who must get his idealised version of what was supposed to be the case for the series "Sanji shouldn't get coc and be capped at admiral level eos, or this series is shit"