Lol I voted RS even though Zoro is my favorite OP character...this isn't about Zoro vs Sanji. It is about what absolutely makes sense. The point is even without Enma Zoro is training his Haki. He will be training his Haki for the rest of his fighting life. With or without Enma. But Sanji...he was so mad he didn't get the invisibility fruit suke suke no mi? I forget what it was called. But no matter how ninja you are you cannot train to become fully invisible. By extension, ACoA can be trained for too. A lot of this crap is just working hard to get your gains but the RS literally provides a skill that is near impossible to acquire. And to top it off it raises all your stats too. It's almost cheating lol. The Raid Suit still has my vote.
Oh yeah, it is probably important to point out that even with a Raid Suit it will not make sense for Sanji to not still hone his haki. In fact I can see him using the Raid Suit to increase his CoO. Like cetacean echolocation or something. See the image. Feel the image. Guess we will see in future fights.
There you go, you proved my point.....

JK...
But thats exactlu why i am biased against the RS. I am not gonna debate that its not an upgrade, cos it surely is. But its not a well suited upgrade for Sanji, simple because hating his family has also shaped his character, and suddenly accepting tech from them does dilute it.
I am not sure how will RS upgrade his CoO.... We've already seen Sanji show immense skills at using CoO, more than Zoro and Luffy, pre Katakuri battle.
Sanji's persona is already one of a handicap, in the sense that he only uses his legs for a fight. I am convinced now that RS is the only upgrade Oda will give him and i dont even see Sanji giving it off to others, like maybe Nami. Thats not happening. But if Jinbei is gonna join and Sanji needs to be in the top 3, this could be the fastest way unfortunately.