I wonder why all of a sudden the cables to be compared have to be equal in R/C/I, RFI, whatever, I thought the point was that all cables sound the same, for instance Ocos and Isolda, standard PC and Eupen, and this is not a shot at Michaelab, it is just because they have been mentioned recently...
In fact I dont think I ever compared cables with the same characteristics, I assume the differences cause the different sound... 
By the way, I agree that volume match is a must...