Ok, I answer the Question by myself…

Just bought the holy grail plus, to replace the holier grail, main reason: I need room on the pedal board

The Holy grail plus sounds almost as good as the holier grail (I’m talking about the long hall setting of the holier grail!!!) The holier grail sounds more musical, alive, shimmering and so on…

Is there maybe any reason for the better sounding holier grail tzo be found in the different power supply used: 18V instead of 9V?