I strongly recommend David's book.
I will always keep my old copies of Bonsai Techniques 1&2 because I bought them at a John Naka demo in Sacramento when I was first starting out in bonsai. He was a wonderfully kind man and did a lot to expand interest in bonsai across the US. But I don't refer to them any longer for information on technique - they are out-of-date with respect to how I practice bonsai today.
There is an overlap in content, but it's not 100%. David's book is specifically directed at design, composition and display. It does so at a much deeper level then anything in John's books and explains the concepts behind the main topic much more thoroughly. But it doesn't go into the horticultural aspects of bonsai at all and those topics are discussed in John's books.
Scott