The point is that BG was professionally involved in aviation for his entire career and understood it completely. He was a witness to the political and industrial developments at the time. TB, on the other hand, I feel is doing a different job- cataloguing, archiving, researching, but at a much greater distance in terms of involvement, timing and breadth of vision. He does it very well, but his is not polemical, argumentative and incisive. Also BG was very careful with his research too.