When something smaller would do
A written document beats a webinar whenever the content is the point rather than the moment. A well-structured page can be read at midnight, searched, corrected quietly when something changes, and forwarded without explanation. A live hour cannot do any of that, and a recorded hour does only some of it. If your material is reference, a document is the honest choice and you will save the afternoon.
A recording beats a webinar when nobody needs to ask a question and no shared moment is required: the training module, the process walkthrough, the explanation you give repeatedly. A live session is justified by precisely two things, liveness and a room, and if neither is load-bearing you are paying for theatre. Conversely, when people will want to ask, when the content is time-bound, or when gathering the audience is itself the goal, the webinar earns its hour in a way a document never could.