It's really not even all that close.
People generally either love Diaz or hate him. Both sides watch, and either root for him or against him. It's tough to find a neutral on Diaz. As much of a 'headache' he may seem to be to outsiders, he is a salesman. He's a lot like Chael but they appeal to the exact opposite groups and repulse the exact opposite groups. But they both always be sellin.
As for Ronda, from 90% of what I read on here, people either love Ronda or ignore her, because they seem to think they know what's coming. It'd help for her to have an epic career defining fight. She's like a 2 minute pop song that some fans are starting to get sick of seeing.
That said, she's still a really good draw in the way Lesnar was, probably bringing buys from segments they didn't have access to before. a great draw and a great front-person to promote and for these reasons, and I totally get why they allow her to duck Cyborg, the same exact way that Tito doesn't get it, and hitched himself to that MMA station-wagon.
But Ronda's not close to the salesman Nick is. Dana can just stand back and let the main event promote itself with Diaz on Board. Ronda sells some but is at her best just being herself, not trying to do too much.