I didn't read all of the post but I would point out that the biggest determinant to egg flavour is what the chickens themselves eat (ah i see nyleve pointed this out just above!). It sort of doesn't matter what kind they are. High fat diets can create some insane eggs. I listened to an interview with one dude who started letting his chickens gorge themselves (not forced at all, they'll be happy to eat) and he said that the eggs had giant, rich yolks.
of course a downside was that the chickens were slightly more prone to cardiac arrest when a plane flew over, or something. but i mean. gotta break some eggs, right?
