Started birds would be ideal, but when you're talking about breeds that are hard to find....I was desperate for anything when I went looking for the ones that I wanted. Didn't matter if it was eggs, chicks, juveniles, or adults. There just wasn't enough people that had them that were either willing to sell or willing to ship them in any form. Fortunately I found someone that was willing to sell me day old chicks and I spent about 14 hrs in my car driving to get them. It was worth it though and I'd do it again to get the birds that I wanted.I also prefer live birds. I'd prefer to both sell and purchase live chicks/adolescents. The reasons given above are solid reasons. But definitive or absolute statements are pretty hard to validate.
A large number of folks on these (H) threads the last few years have gotten their start through shipped eggs, and from some pretty darn good breeders. There are too many successes to count. The advent of bubble wrap and proper wrapping of eggs has resulted in hundreds of boxes of shipped eggs arriving with the contents visually, in pristine condition. Eggs breaking has become almost a non issue.
What hasn't changed, it seems to me, is the resultant poor hatch rates. The handling of the boxes is brutal on the eggs internal integrity. That issue remains.