If you prefer silver, copper or a mix is entirely up to you. Silver is not "better" for sound. It just happens to cost more. What you like is up to you.
There is no such thing as a "better sound". It's all up to preference. Some may prefer full copper for the Z1R, some prefer silver/copper hybrid, some prefer full silver, some prefer gold. At the end of the day, as long as the choice of material makes your juices flow, that's the only guide you should follow, and of course what your wallet can afford.