For now we only use the YouTube transcript because for most educational content we've found it does about as well for lower cost.
We may make that an option though, since we also offer other resource types (pdf, slides, docs) -> course.
How about comments? Have you tested refining comment threads for useful errata or adding key details?
This maybe doesn't matter as much in the content you're processing now, but see my reply to sibling comment here, where it matters a lot for these niche videos where the creator did not mention or did not know about some important detail of a process or task.