I have the Grey Seal book and both videos. I think that they compliment each other very well. Watching the videos demonstrates several techniques and tricks very efficiently, and the book is a great reference to have at your side while in the process of building. Its comb binding allows it to lay flat at whichever page you need, which is very handy.
The "Nip and Tuck" method is a very interesting approach, although it is one that I have not yet used, and I'm not really certain that I will- my brain simply doesn't work that way.
The first part of both videos is identical, talking about materials and adhesives, etc, and building the mouthplate. But then they go off in very different directions. They show you what you need to know, but much is also left to your creative imagination. In fact, creativity is pretty heavily stressed.
They are very well-produced, and I personally have found them to be an extremely good value for the dollar.
Hope this helps!