Personally, I prefer PDFs and/or Physical Books for learning new materials.
My second favorite is MP3 or other audio files that I can burn to CD and listen to in my car.
Video comes in last for me.
While it can be a good format for somethings that need an actual demonstration, like software tutorials, contrary to popular belief I don't think its the end-all-be-all of media.
Not everyone is created equal, some people have boring voices, thick accents, talk too fast, too slow, are too excited, or not exciting enough.
With video there are just too many variables that can get in the way of the content if you're not working with a professional production company.
I really hate sitting through 20 minute Camtasia fueled borefests, when the same guy could have easily gotten his point across in 2-3 pages of written text.
Please vote and discuss...