What's the benefit of consuming complex carbohydrates (grains mostly) over simple carbohydrates (fruits, veggies)?

You got it backwards: Fruits and veggies are NOT simple carbohydrates! Simple carbohydrates are sugars and foods that easily break down into sugars,such as white flour,white rice, potatoes and juices.These readily raise our blood sugar, which is unhealthy.Complex carbohydrates are found in whole grains,most vegetables and fruits and generally contain fiber. These raise blood sugar less. See http://tinyurl.com/y8f4cagu