If we can't get fresh pastured eggs from local farmers (my first choice), I buy pastured from my local health-food grocer.
Pasture raised eggs from reliable farmers are allowed to roam free- eating their natural food sources of plants and insects. What this leads to is more nutrient-dense food for you! Pastured eggs contain 2x the amount of omega-3's, 3x the amount of Vitamin E, 7x more beta carotene and 6x more Vitamin D as their conventional counterparts!
'Free Range' is only regulated for poultry-produced meat; not eggs. Legally, free-range simply means the chicken has access to the outdoors for unspecified amounts of times. It could be just a few minutes or outdoors in a 2x2 box where it lives it's life laying eggs. There is no regulation on feed for free-range chickens either which means they can be fed (and likely are) with feeds fattened with toxic crop oils and other unhealthy fillers. If you eat the egg, you ingest these toxins.
'Cage-Free': means the chickens are raised without a cage but tells you nothing about their living or feeding conditions. They could be raised in an overcrowded, stressful space on a factory farm pumped with hormones to lay bigger eggs. Again, the regulation is nill here.
'Organic': if you can't find pastured eggs, get organic. Organic eggs are regulated by the USDA and farms must be certified by feeding with non-synthetic feed made without pesticides. Animals must have access to outdoor spaces. Again- this doesn't regulate how long the animals are outdoors or other living conditions but it's certainly better than the above two options.
TIP: Most cage-free and free-range eggs are light yellow in color- an indicator of nutrient deficiencies in the birds. Egg yolks should be bright orange in color and creamy in texture (and absolutely delicious!)