Eggs Labyrinth

"Free range" refers to chickens being allowed to range freely outdoors where they can eat whatever grass, weed seeds, insects and worms they choose. This results in more nutritious eggs and meat for consumers, and more healthy, humane conditions for the birds. Some producers abuse this term and label their eggs as “free range” when in fact all they have done is open a door to allow their chickens to range in an outdoor area of bare dirt or concrete, with no pasture in sight. 

Thus you need to confirm if your eggs or chicken comes from "true" or "pastured" or "grass-fed" free-range conditions. Also, some producers choose a modified system that involves keeping birds safe from predators by confining them in pens or inside electric fencing, and moving the pens frequently onto fresh pastures. Thus, pastured birds may be true free-range or penned, but either system is correctly referred to as “pastured.” And either system is a better choice than products that come from industrial factory farm conditions.

See Egg Nutrition Comparison Chart
http://www.motherearthnews.com/uploadedFiles/Eggs%20chart.pdf

An analysis shows that free-range chickens raised on pasture produce eggs with as much as six times as much as the hot nutrient of the moment, Vitamin D, according to Mother Earth News, which performed the nutritional testing.

This is on top of previous research by the magazine, which showed that the pasture-raised chickens produce eggs with:

1/3 less cholesterol
1/4 less saturated fat
2/3 more vitamin A
Two times more omega-3 fatty acids
Three times more vitamin E
Seven times more beta carotene
Read the full report, More Great News About Free-range Eggs.

But be careful. Free-range egg labels are notoriously misleading because the laws governing the use of the phrase are very slippery. Eggs can be labeled "free range" even if a door no chicken uses is left open a certain number of hours per day, and even if that door opens onto a dirt or concrete expanse. Look for true pasture-raised chickens -- or ask your local farmer or backyard chicken enthusiast if her chickens can peck around at will in nature.

http://www.motherearthnews.com/Natural-Health/Health-Benefits-Free-Range-Eggs.aspx