The complete diffrence in how Zoro and Sanji were introduced just reinforces that Sanji, while still probably the third strongest in the crew, is now a full-time gag character and Zoro is the bad-ass First Mate
As a Zoro fan I like were he went but I still feel bad for the Sanji-lovers out there….
Sanji is a fairly important character from a narrative perspective. Oda has always used Sanji as an "anchor" of sorts to tell the story. For example, in the last two chapters, actual story advancements are done through Sanji's character (as he had the most pagess?)
He's versatile as a story device because his character is 1) comical 2) rational and highly intelligent and 3) the third best fighter on the crew.
Sanji related - did he switch parts in his hair because he can Hell Wink?