Bomarc,
I agree that there may be no difference between XRCD and K2, but I specifically recall comparing the notes on 2 versions of Sonny Rollins, Saxophone Colossus. The XRCD one, which I am holding as I type, says:
XRCD mastering - Alan Yoshida under supervision of Akira Taguchi (A&M Mastering Studios, Hollywood).
Although I no longer own it, I am certain I compared this to the notes on the Prestige 20bit K2 version and it was digitally mastered by someone else. Does anyone out there have the Prestige 20bitK2 version? If so, can you confirm this?
Having said that, I, like you, have yet to be convinced that there is a real difference.