The Stratesave compare function compares complete directory structure, file dates, attributes, security, in addition to simply file data. It also reports files and directories which have been added to PC. For registry hives, it optionally lists all added/changed/removed keys, if compare option Compare registry keys is set. You can now compare the actual state of your PC with the state at the last backup. For example after installing some downloaded Software, you might want to know about what changes this Software has made to your system.
Please note that this is an advanced feature, and requires some knowledge to interprete the result list. After some heavy system activity or after a reboot there will be a few registry changes which are also reported.
See also: How Stratesave backs up the Registry