I would say it's less than 50/50 at this point, maybe around 30% at best. But saying Usopp has more chances of getting it is nuts, considering what we know about CoC. Usopp could get it but Sanji's chances of having it are much higher. Whether people like it or not, CoC is a warrior trait and in absolutely every group in the story, CoC is possessed by the ones who are at the top of the hierarchy, those who are the crème de la crème of their faction.
That's why BM and Katakuri are the ones who have it in BM's crew, or Roger, Oden and Rayleigh in Roger's crew. Sure, there are characters like Shanks, who wasn't among Roger's strongest men despite being a CoC user, but he was just a kid far from his prime back then. Do you expect Prime Usopp to be a greater warrior than Prime Sanji ?
As for Yamato, she's overhyped as usual, saying she might have CoC because her father has it makes sense, but using a theory based on another theory (Yamato having CoC and her joining the crew) to dismiss the possibility of Sanji getting it is nonsensical.