In my opinion, the research behind these releases: Sourcing the original material, recovering the order of recordings, documenting each session in detail (who, when, where...; often a complete discography for a certain artist and label) in the enclosed booklets, requesting extensive comments (far beyond traditional "liner notes") from experts, sourcing photographs from the recording sessions. Most of the time, the mastering is also very good. Do yourself a favor and try a set. You won't be disappointed.