i switched from SCCS to RCS many moons ago. the set of facilities that RCS provides is a proper superset of the facilities provided by SCCS. in my opinion key advantages of RCS over SCCS are:

• in addition to providing version control, RCS provides very flexible configuration management facilities. (configuration: set of versions of files that make up a release/snapshot of a software system). it provides both selection and composition mechanisms for configuration management. RCS can manage multiple configurations.
• provides facilities for merging updates from released configurations into the main development branch and vice–versa.
• provides automatic identification. (identification: stamping revisions and configurations with unique markers that unambiguously identifies the configuration – and recursively so.)
• can control access control to be strict or loose.
• can provide access control beyond unix file protections.
• provides very flexible tools for pruning and maintaining an ancestral tree.
• provides user definable states to manage conflicting updates.
• tools (tried and proven) exist to manage multiple ancestral trees.
• tools exist to manage multiple directory hierarchies that make up a software system.
• RCS software runs on multiple platforms, including lots of non–unix ones.
• RCS's delta storage method is both more space and time efficient than SCCS's. (reverse deltas as opposed to interleaved deltas).
• its much better integrated with make(1).

if you need further info, documentation, references, statistics, or just want to shoot the breeze please drop by.
cheers, bammi