In general, long grain rice is lower GI than short grain. Slightly undercooked rice is lower GI than over cooked. "Parboiled" rice (such as Uncle Ben's) is consistenly lower GI than other more traditional rices. Sushi has a GI of around 50% (on the glucose scale), and brown rice is not necessarily lower GI than many white rices, but it has fiber and vitamins that are not found in white rice. The lowest GI rice you can eat is called "high amylose". If you're worried about GI, then I recommend you stick with the high amylose white rice and don't overcook it. Adding vinegar or lemon juice (such as found in sushi) will also lower the GI of your rice.