The difference between brown rice and white rice is that the hulls haven't been removed from brown rice. White rice has been "polished" by having the hulls removed and often washed.
Organic brown rice isn't likely to have been washed, milled or treated so dirt and pests may not have been removed.
Most American produced white rice has been washed and enriched so if you wash it at home you remove nutrients that have been added. I always wash foreign-produced white rice.