Ideal is both. Text with pictures is much more convenient, but sometimes a video captures something that isn't explicitly discussed but nevertheless useful - "Where does that tiny spring attach?" You might scroll through the video and find it while the narrator is showing something else.
Videos with annotated and labeled chapters or markers are excellent - it's not so hard to navigate, and you can see the actual action being done.
Thank you for even discussing DIY repair - I find it extremely frustrating that 90% of the "advice" offered about any mechanical malfunction is "Send it to Don Goldberg."