I agree with daveyf about the basic sound character of the Kleos vs. the Koetsu Black. Something is odd about the setup if the Black sounds more clear but lacking in bass (it could be the original setup with the Kleos was off).
As to which cartridge should sound better, that is a matter of taste. I don't think modern vs. old design is as much an issue, given that basic design of MC cartridges has not changed much.
As to which cartridge should sound better, that is a matter of taste. I don't think modern vs. old design is as much an issue, given that basic design of MC cartridges has not changed much.