Most of the eggs currently sold in supermarkets are nutritionally inferior to eggs produced by hens raised on pasture. The 2007 Mother Earth News egg testing project has found that when compared to official U.S. Department of Agriculture (USDA) nutrient data for commercial eggs, eggs from hens raised on pasture may contain:
Source: http://www.motherearthnews.com/eggs.aspx
Cage Free vs Free Range vs Pastured Eggs
Cage Free - cage free chickens generally don’t ever see light of day and are cramped into small quarters with thousands of birds.
Free Range - the definition of a free-range chicken is that the henhouse only needs to have access to the outside. Many free-range henhouses have a small door to an outside paved area that is the size of a small dog run, and devoid of plant material and bug life for them to forage on.
Pastured Chickens - pastured chickens are raised on open pasture and allowed to forage on their natural diet. They are exposed to sunlight, plants, and bugs; which helps them produce highly nutritious eggs. They are getting Vitamin A, E, beta carotene and omega-3 fatty acids from the plant material and Vitamin D from the sunlight.