I have lots of books. I have lots of DVDs.
I have watched all the DVDs. Some more than once.
I have not read all the books. I still have a far too large number of unread or only flicked through ones.
The hope is that the mere possession of them will make me a better player
In terms of learning effectiveness, due to my age, my chess knowledge has really come from books, as the DVDs came along at much much later stage in my chess development. No idea what it would be like to have tried to gain the knowledge at a chess fledgling age from DVDs (plus to a similar effect the many and varied chess material you can get online, either free, or paid for on sites like ICC). A lot of the free 10 min vids are like chess popcorn I can lazily munch through, but are they nutritional for my chess
I kind of view the DVDs more as an entertainment factor, rather than to gain knowledge. So if I happen to learn something, that's a bonus. I found Kasparov's DVDs on the QDG and Najdorf very interesting, but very probably wouldn't play either. I found Korchnoi's DVD rather entertaining.
I feel the zeitgeist is very lazy nowadays, and book study feels like hard work, but I think hard work gives the best rewards.
I've bought some opening DVDs just to get a feel for if I might be interesting in playing an opening. If they were all accompanied by analysis files, like e.g. Gustafsson's 1. ...e5 repertoire, this might be the way forward.