I've recorded various Pluralsight videos, and some of my conference talks are online too. I think it's important that there are lots of different media available for teaching, because people learn in different ways.
Personally I find reading (whether online or - less often these days - in book form) more useful than videos for most things, but I know it varies.
I do think there's a lot of benefit in a structured approach to learning when you're a relative beginner in a topic, instead of learning piecemeal. I'd expect a good online course to do that in the same way that a book does, but there's less benefit in watching lots of different, uncoordinated videos, each on one different language feature, for example... each video may assume a different amount of knowledge beforehand, use different metaphors etc. With a structured, ordered approach you can build from one topic onto another.