Regarding the Mercury Masters box: I own most of the box as content of the three Mercury Living Presence cubes, and owned many as individual MLP releases before that. The recordings and performances are all cream-of-the-crop, even though some be mono. And with Tom Fine (son of the legendary Wilma Cozart Fine, co-producer of the original recordings) in charge of the both audio (remastering) and documentation this is a no brainer. You cannot go wrong. Regarding the Decca box: I own everything already, either in prior Decca Legends, Eloquence, or Tower Japan releases. All are very good to excellent recordings but not quite as special as the MLP stuff. I did not order the Decca box, but I would not hesitate to do so if I did not already own all or many of the recordings.