This latest version of Silverlight delivers hundreds of features and controls that, when combined with the continued innovation in Microsoft’s world-class tools for designers and developers — Microsoft Visual Studio and Microsoft Expression Blend – present the leading edge in rapid, powerful application development. With printing support, rich reporting and charting, and integration with back-end systems and server products including Microsoft SharePoint, Silverlight is ready for business.

With

Silverlight you get cross platform (almost all browsers on Mac and Windows) .NET runtimes, where WPF is Windows only.

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With WPF (XBAP), you can not script against it or have your XBAP