This article explores what "portable" Visio actually is, the risks involved, and the modern, safer alternatives available today. Does an Official Visio 2010 Portable Version Exist?
This version introduced the "Ribbon" to Visio, making it much easier to find tools and templates. Intelligent Diagramming: Features like Quick Shapes Auto Align Auto Space microsoft visio 2010 portable 64 bits
The short answer is:
Ability to link diagrams to live data sources like Excel or SQL Server. This article explores what "portable" Visio actually is,