Chris Parkes sent a mail round internally telling us about MORE resources & demos etc available to partners. Chris has written about it on his blog (discovered this after I wrote this - here, there may be some comments on his worth reading, so double check!!)
The Demo Showcase has been extended to include Deep Dive/Product virtual environments *which are available to all partners* Only Demo Showcase remains as the Gold/Cert benefit moving forwards...
The following are now available for immediate download:
2007 Microsoft Office System
- 47 Hands-on Labs
- 25 demonstrations
Microsoft Forefront and System Center Demonstration Toolkit
- Microsoft System Center Configuration Manager
- Microsoft System Center Operations Manager
- Intelligent Application Gateway
- Microsoft Forefront Security for Exchange Server
- Forefront Client Security
Microsoft Business Intelligence Demo (Data warehousing, reporting and analysis, performance management)
- Microsoft Office PerformancePoint Server 2007
- Microsoft Office SharePoint Server 2007
- Microsoft Office 2007
- Microsoft SQL Server 2005
Download location is here:
https://partner.microsoft.com/global/salesmarketingsection/smsalesdemos/sdproductdemos
As for the difference between the two, the web site says:
"This collection of Microsoft software product demonstrations is designed to complement the business-scenario-based Demo Showcase sales tool. These demos illustrate product-specific features and functionality in detail, while the Demo Showcase tool helps illustrate how a full range of integrated Microsoft software platform solutions work together in business scenarios. Use the links in the table to download or order the product demos you need."
However I was able to access the demo content online at https://partner.microsoft.com/global/salesmarketingsection/smsalesdemos/sddemoshowcase - perhaps as I am a SBSC partner!! 
ttfn
David