Now that Republican Donald Trump and Democrat Hillary Clinton have won their respective party's nomination for November's presidential election, security experts are assessing which of them would be a better choice for Japan and other U.S. allies in the Asia-Pacific region.

At this point, Clinton, a former secretary of state, appears to have an edge over Trump, a business mogul and political outsider, given her deep understanding of the importance of alliances.

Trump's threat to pull U.S. forces out of Japan and South Korea unless they contribute more to the costs of their defense makes U.S. allies "nervous" and gets China, North Korea and Russia — countries that apparently do not wish to see firmer U.S. engagement in the region — "excited," according to some of the experts.