One SEO professional asked John Mueller as a follow-up to a Schema question mentioned earlier in the hangout: wouldn’t competing Schema not be a good thing?
John explained that yes, that’s what he was meaning there.
If you have different types of rich results, which cannot be combined, then Google’s systems just have to pick one.
And if you have a preference, which one you prefer, then John would just make sure that you just have that.
This happens at approximately the 43:17 mark in the video.