The 4K improves the video quality over the Blu-ray. The yellow brick road looks yellow and not a darker yellow [for example]. The disc also includes a "making" at around 50 minutes hosted by Angela Landsbury and taken from TV at one point. The regular BR contains various versions of the movie in addition to a 61 minute "making" - not the same as the 4K one with some repeated information. There is also some shorter featurettes.