I was going to suggest trying to contact different colonies, but that had been covered so just have to address the idea of the best egg, I didn't bring it up so it's not just me going off topic. My preference is a lighter coloured yoke, which is milder in flavour, I think I ate far to many grasshopper fed chicken eggs when younger, and some of those were pretty stong as far as taste.
As for which egg is better as far as health, I'll post a link, but remember everything you read can sometimes be not 100% true. In the link there were two things that I considered opinion not fact, one was there is no difference in eggs, the difference in taste proves there is a difference. The second had to do with the beef comment, the author should maybe do some reasearch on beef before making that statement.
http://content.time.com/time/health/article/08599200233400.html