About thread's topic, let's take a look at canon and factual evidences.
One of the latest example is a SBS question regarding which DF to give to the SH.
- Oda gives Zoro one of the strongest mythical zoan DF, which enhances his ability.
- Oda gives Sanji a DF that not only doesn't fit many of his abilities, it also slow him down.
Another example is from an arc I don't like pre TS, Thriller Bark.
- Oda can make Zoro and Sanji both have a nothing happened moment together, as foreshadowing and example of why they're the Wings. But Oda only gave it to one of them.
Or, random examples from post TS arcs :
- Sanji's hate mostly come from his FI nosebleed, in the same arc Zoro oneshot arc main antagonist.
- Sanji is the one who saved Tashigi in PH, but she instead has a moment with Zoro.
- Sanji gained Viola and her info, but it got downplayed and nodiffed by Doffy. Zoro stalls an Admiral and showcase one of his greatest sword slash.
- Sanji's pairing got separated from him and memories erased, Zoro's pairing slept with him.
It's clear as day which one Oda favors, I don't know what this thread intends to do.