Interesting question and I'll be very interested to see what others have to say as well.
With regards to video tutorials, an usablity study found that, most new users prefered watching the video tutorials as opposed to scanning the text.To quote the article
Only a few of the users read the help. Most just watched the videos.
Keep in mind that all of the users were brand new to the app.
With one user, he didn’t realize there were videos at all, as I had
them buried in a side option called “screencasts.” Screencasts seemed
something similar to screen sharing, he said, so he didn’t click there
until later. When he did, he felt that the videos were just what he
was looking for in help material.
Another user watched one of the videos twice, and after watching the
video, was somewhat successful in completing a task (or at least a lot
more successful than before — there were still challenges).
However the same study has this to say on the intermediate and advanced users
Intermediate Users Skip Videos, Scan Text
Despite the popularity of the videos, I found that videos appeal to
different users in
different contexts. For more tech savvy users just looking for an
answer to a specific question, they were less likely to watch a video
and more likely to search/scan the text for answers to their specific
questions. Even so, these intermediate users were interested and
encouraged by the videos available and sometimes watched one.
Coming to why video tutorials might be more useful for new users
- It allows you to visualize the content in a dynamic way and see the steps before you do them yourself
It helps establish the sequence of steps which should be done. For example, if you were just trying add a blend to a layer in photoshop, the written steps would
- Open photoshop
- Open the new image
- Add a new layer
- Right click on the new layer
- Select Blending options
- select the blend option you want
- set the settings as needed
- Click on save
note: I wrote this from memory so dont catch me if I made a few mistakes :)
Taking the above example,there are so many cases where a new user could get confused (e.g. How does he open a document in photoshop or how does he add a new layer or so on). In this case a video would be so much better as he can visualize each step of the process and do it in parallel
For an advanced user, the advanced user might be just interested in what settings have to be set for the blend mode and the text instructions would suffice for him as he knows where to look.