Im not sure what you mean by a burned digital copy but 4K UHD disk is inherently superior to streaming. In particular the audio is lossless on disk, but is only DD+ (sometimes with Atmos) with streaming services. There are no UHD downloads.
With UHD films on Itunes the bitrate is high enough however for the picture quality to be hard to distinguish, especially 4K restorations and recent film releases and they are sometime in Dolby Vision too. This means they are a great way of watching films as the price is often a lot less than UHD disk.