Just going to say that from the position of someone that uploads videos to YouTube semi regularly and that has both read and watched a good number of tutorial type of things in general the subject is very much part of whether one or the other can work. The thing with Minecraft is that it has a few thing which together means you get both end of the spectrum without much in-between.
Because Minecraft is a 3d space that can have complex side dependent effects, things like which side scrap goes in a massfab and what end you hook the pipe to a transposer, means that a video is a good tool to show whats going on as it allows a better sense of how things go together way beyond what even multiple pictures can show. Because Minecraft is a game of crafting with what are sometimes very fiddly bits, things like all the different bits of plate things that go into a Redpower circiut and the multistage confusion that is nuclear generator, means that unless a video is a bad tool to show off a mod as unless you really prepare ahead of time you can end up just trying to remember where you put that one bit or didn't do that one step. These 2 things cause both high and low quality videos to appear but there is one other factor to why videos seem to be of lower quality and that is there are actually very few tutorial videos.
For instance I don't think Direwolf has a single tutorial video. Not a one. What he does is mod spotlights and his lets plays. The mod spotlights are meant to inform you of a mod and while he does generally go over whats going on in the mod in a tutorial sorta of way its not meant to be a tutorial but rather a thing to let you dive into a new mod or update you to an old mods new features. His lets play on the other hand are not and have never been even close to something you could call a tutorial but its where I learned most of what I know of for a majority of the mods I use. He just builds things and explains it as he goes so if you like his videos you will pickup quite a bit about the mods as he goes without having to actually "learn" it. Anyway yeah, I was going somewhere with this before I turned it into an add for Direwolf, oh yeah, basically a lot of things people consider tutorials are mod review which shows the features of the mods without actually attempting to truly teach you how to use the mod. If someone actually sat down and got it together they could make really good tutorials for Minecraft. Anyway wikis and such are dependent on the community to fill them with content so unless its maintained by the mod author or avid fans its going to be about the quality of a YouTube video but with text, we are just lucky DF produced and attracted the kind of people who could keep its wiki updated or I bet a lot of us would not be here on this forum cause of how hard it is to figure the dang thing out well enough on your own.
Edit: my goodness, this turned out longer then I though...