My grandmother lives in the country and the chickens she has lay eggs in which the yolk is much larger than store bought ones. This could be due to the breed of chicken(I imagine theres different chicken races...ask suckmymuscle for more info) or because the lack of steroids. I know this doesn't answer your question at all...
good day!
ROFLMAO!!!
Seriously, my friend at work just gave me some eggs from her neighbors' chickens. They've got a tiny chicken coop in their yard in the city, which I find somewhat amusing. Anyway, the egg yolks appear much darker than the "standard" store-bought variety. I suspect it is due to the feed and/or, as you pointed out, the hormones/lack thereof. They also taste a little different, though I don't know if that necessarily translates to better...just different.
Eggland's Best claims that the chicken feed they use yields eggs with "25% less saturated fat, double the Omega 3, ten times more Vitamin E, compared to ordinary eggs."
http://www.egglandsbest.com/Somebody should ask Minspin to run some lab tests on the damn things. I'd love to know if it's all legit or bullshit.