Not that this answers the original question, especially when you said you wanted a comparison between:
Royal Master Piano Black vs. Royal Master Corian - difference?
Royal Virtuoso Piano Black (if available, not sure) vs. Royal Virtuoso Corian - difference? 
Melville's response actually provides information on a 3rd comparison: that between the Master and the Royal. As I said in a previous posting, in the older version of the Royal Virtuoso, the cabinet was only partial Corian and it was in fact "black" on parts of it compared to the newer version which is all Corian.
So now I guess we have the full answer to which is best:
#1 Royal Virtuoso - newest all Corian version
#2 Royal Virtuoso - older version, partial Corian finish
#3 Royal Master - discontinued, partial Corian finish
I guess you now understand why your original message was somewhat cryptic and could be interpreted a number of ways. Anyway, was just trying to help.