First of all, this is a great thread and for once it is good to see some nice things about both characters from both fandom. I have tried to create a similar thread but I didn't seem to describe it well.
https://worstgen.alwaysdata.net/forum/index.php?threads/luffy-zoro-sanji-appreciation-thread.1263/
Props to you
@Akai2 for making this thread more elaborate and descriptive.
I am hardcore Luffy fan and then I am more of a Zoro stan than Sanji. However, I supported Sanji on few occasions about his decisions like whatever he did during WCI (though it left bitter taste of him kicking Luffy like that) and his PL feats.
Now, coming to the point. Both shares some good traits
Both has good character designs and looks cool compared to Luffy (Luffy looks cool only in very serious moments).
Zoro has best one liners and most badass moments and Sanji has best brainy moments.
Both understands each other without saying a word and their teamwork is impeccable.
Even their fighting forms look cool and stylish.
Contrary to popular opinion I like RS Sanji however, I wan his epithet remains to be "Mr. Hunter". I am waiting for more of his Mr. Hunter moments.
Anyways, I will post more if I remember anymore.