SCORM overwrite existing vs new version

Summary

What's the difference between overwrite existing and a new version when uploading content

Content

I have tested the Overwrite existing vs new version when using the SCORM Importer in Taleo.  I notice both keep the same class and create a new SCO with the same name and different dates.

Does anyone know what the difference is then? Does one overwrite user history while one keeps it? I cannot see a difference.