Oda loves Sanji.
I can tell that because of the way he writes him or the way he characterize him or the way he makes him evolves.
Zoro is the strong, the honorific the willpowered, but Sanji is much deeper, he is the representation of masculinity in all its glory (and all its failure also).
Sanji is far from being a perfect written character, but there is something deep in the way Oda writes Sanji and should I say.. personal. In a way, I could easily see Sanji as the character Oda is the closest with.