Are silver coated cables a bunch of hype?

I'm looking to upgrade some cables (digital coax/comp. video), and I've seen recomendations re: Canare. Originally I looked into a few silver coated copper cables. I spoke to a tech at Canare cable and he said none of their cables are silver coated, and that silver made no difference when it came to signal transfer. Is a good quality copper cable as good or better than a silver coated cable? Does the silver coated copper have a cheaper copper grade/purity to cut cost when adding silver? Thank You, Chrisrn.