I have prepared a comparison among the three commonly used Version Control Systems Visual SourceSafe (VSS), CVS and Subversion.
The weights and scores are based on my judgement. I think this type weight scores based comparison may help you in convincing people (e.g. your project team, colleages, senior mgmt in your company) to use Subversion.
Subversion : 251
CVS : 171
Visual SourceSafe(VSS) : 138
Check it out at Comparison of VSS, CVS and SVN