I prefer reading books. It lets us go at our own pace, can re-read parts not understood. Moreover with eBooks it can be interactive with visiting links shared in the book. Videos with duration of 40mins or so are difficult to follow because its often hard to concentrate at a stretch for that duration. And also there may not be logical separation in the videos. But with Coursera introducing short videos, those are really easy to follow. Books can be carried around and read at leisure.
Videos are none the less explanatory depending on the quality of content and the speaker.
For me, I don't think either books or video work. Although I used to read technical books very early in my career, I gave up reading those because I just couldn't multitask. As for videos, I can't watch any video (other than movies) that last for more than a few seconds. I think for me audio based learning might work the best. I keep listening to technical audio podcasts and at the same time do some other tasks and so far I have found it better than the other 2 options.
I've done a few online courses, some of which used the kind of short videos mixed with quizzes that Jeanne described in her blog, and I found this approach worked well for me. It was also very flexible, as it was easy to sit down to study for, say, half an hour and still feel like I was making progress in a structured fashion. But this positive experience also reflects the quality of the teaching materials themselves, not just the format.
The key thing with video lessons is that they should be designed specifically for the format. I find conventional video lectures - where they've simply filmed the classroom lecture - tend to be much less useful for active learning, although they can still be helpful for getting an overview of a topic, and of course some topics require more time in order for the teacher to be able to explain a particular point adequately.
Books are good for reference and for providing greater depth that you can absorb in your own time. They also allow you to read around a topic i.e. going beyond the focus of a video lecture. At the same time, it can be hard to learn some things from books, as you need to be pretty disciplined not to skip the topics that seem hard or irrelevant, unless you're working towards an exam of course. Right now I'm studying statistics for a university course via books, which is hard work but I'm lucky to have excellent course materials that are well-structured and provide plenty of practical exercises mixed with the theory, so I don't feel videos would be any great benefit in this case.
I also find reading and learning from printed books much easier than reading/learning from the same materials on a screen. Not sure why that is, but maybe it's a generational thing as I'm old enough to remember the world before PCs!
Finally, it also depends on what you're trying to learn anyway e.g. practical skills like programming require a mix of approaches, where good books and structured learning materials (video or print) can be very helpful, but you still need to apply what you're learning as well.
It might partly have to do with the fact that I'm not native English speaker and I don't practice conversation a lot, so following the audio track is a bit too hard for me (and there aren't much technical videos in my native tongue available). It is much easier to use dictionary when reading text, either online (a single-click for me), or offline. Turning to a dictionary when watching video is a nightmare, not least because of the nice English custom of not having any relationship between the spoken and written form of a word.
But far more important for me is that I'm used to re-read the lines, sentences or paragraphs I've got troubles understanding. In a book that is easy, returning one sentence or paragraph in a video is very cumbersome. Similarly, if I'm not completely new to the topic, I can be tempted to skip the easy parts (and return to them later if they turn out to be not so easy ), which, again, is difficult with video.
Moreover, I believe that creating a good learning video is far more difficult than creating a good book or article, so it should be easier to find good books and I don't even bother trying to find good videos. (That might change as soon as Google finds a way to index videos by their content.)