Two large Harvard studies documented what we have known for a long time about whole grains. Regular consumption of brown rice resulted in a much lower incidence of diabetes than white rice. This has a greater significance in the orient, where rice can consist of 75% of the diet. But it is also relevant in the US, especially since a growing number of people have celiac disease or an intolerance to many grains. Rice is usually tolerated for such people, and brown rice is definitely the way to go.
See Arch. Intern. Med. 2010;170:961-9.