Right now, as things stand, your history on VC6 begins from the time of your organization or property's first sign-up. You had no access to Security & Surveillance Information Network (previously SIN) alerts prior to when you signed up. However, with VC7, you now have access to SSIN alerts all the way back to 2001, when the first SSIN alert was sent out. You can also search against those historic SSINs, as opposed to only the SSINs that you've received.
In addition, as SSINs do not get dowloaded onto your local server anymore with VC7, you don't have to worry about space and can use that freed up space on your server for other features, like an expanded CID or X-LST/PDE.