Do you find some of diamond methodologies more compelling than others? Which, and why?

Jaret Diamond's Guns, Germs, and Steel has generated a great deal of controversy throughout a number of academic fields; there have been many editions printed and many counter-arguments written. While the topic of the book is historical in nature, Diamond himself is not a historian, but rather an ecologist, a scientist who studies nature.
As such, his arguments about nature, ecology, and physical geography as an determinant of progress are quite convincing. One of the key claims he makes is that in the history of Earth, only 14 species of large mammals have successfully been domesticated. European, Asian, and some African civilizations had access to many of these large animals, most importantly cows and horses. By contrast, Australian civilizations had none of these, while South American civilizations only had llamas. As such, European-Asian-African civilizations could utilize this animal power where many others could not.
Another convincing example Diamond lays out is how physical geography creates or destroys cultural unity. He contrasts medieval China with medieval Europe, demonstrating how their populations are both culturally and ethnically fairly similar. Yet medieval China was rarely more than one nation along its broad coastline, while medieval Europe is composed of dozens of nations that are divided along its peninsulas, islands, rivers, and mountains. The geographic schism in Europe increased competition for spare resources; the geographic unity of China led to a large homogenous society with little interest in its neighbors.