Quinoa is a gluten-free superfood seed closely related to broccoli. One of only two complete vegan proteins (the other being hemp), quinoa contains a hefty amount of lysine, an amino acid not readily found in vegan diets. Quinoa contains a huge amount of protein and other nutrients per calorie, making it a far superior choice for vegans than brown rice. It is also low glycemic and highly alkalizing.
The main nutritional drawback to quinoa is that it contains saponins, a naturally-occuring toxic pesticide that the plant produces to ward off birds. Remember that plants are Darwinian creatures too, with no special desire to be eaten! You can mitigate this risk by washing your quinoa thoroughly or buying pre-washed quinoa.
The are some serious ethical questions surrounding the not-so-fair-trade manner in which quinoa is grown and harvested. Due to its popularity, the price of quinoa has soared, meaning that native peoples in South America where it is grown can no longer afford to use it as a staple food.