I only did half of the video-tutoring task (I tought Ted about Emacs org-mode), because we were a 3 person group and I was on holiday leave until it was due, so scheduling was a bit difficult. So my perception of both ways of teaching might be a bit skewed. Plus I don’t have much experience teaching people at all.
I do think it makes a difference whether one looks at it from the perspective of the teacher or the student. If I were the one teaching I’d prefer to do a video-conference and explain directly, because of all the reasons that were already mentioned: mainly because it is easier to react to peoples different levels of literacy, and it is possible to answer questions directly, which also helps to gauge how well whatever was taught was received. Also, I think preparation time is less, since if you know what you are talking about it’s sometimes possible to just ‘wing’ it, you don’t need to think as much about structure than with a screencast.
Then again, screencasts scale much better, so it is only a one-off time investment, while one needs to give a tutorial every time again and there are limits to how many people you can teach. So, I guess it really depends on the context which one is better. Also, I think the practicalities shouldn’t be underestimated. As we’ve seen, scheduling those tutorials can be a right pain. And, I think I’m not the only one who is used to the usual 15 minute delay in video-conferences. The 15 minutes it takes until everybodys’ audio/video is working. And every now and then it doesn’t work at all.
Also, screencasts can be viewed whenever it suits, which is the main reason I’d prefer it if I am the student. On a sidenote, depending on the topic I’d usually prefer a written tutorial, where I can copy and paste examples and code pieces. If time is not an issue, I’d prefer a one-on-one lecture though. Especially since I regularly catch myself checking my email or doing something else while watching screencasts…
To summarize, I think if everybody involved has enough time, a video conference would be my preference. If that is not the case, screencasts are a “good enough” alternative.