The advantage of CyberCash is that the system is similar to credit card payments which are well understood by the public. In the US, almost everybody has a credit card. It is therefore evident, why many people feel comfortable using this payment scheme. RSA and DES encryption already exist well over 10 years and are proven to be secure.
One concern about CyberCash is anonymity. All payments become traceable, as the system is based on credit card transactions.