Mike,
Well the developer is trying to hit existing VSS projects.
Personally, having used both, I prefer VSS. ClearCase is a much larger PITA to actually use than VSS is. Some of that may have to do with the way the CC folks here decided to set things up... but to make a change to a single stored proc or a single C# file involves several steps of CC dialogs/wizards, tons of time and megabytes worth of code being pushed onto my machine. Once CC has done it's thing it is pretty handy to be able to do source control by a right click in windows explorer, that's about the only thing I like about CC over VSS.
>I know this isn't the question you asked but have you considered using ClearCase? We used it at one software development company I worked for and I quite liked it.