Silverlight

Here is the list of advantage why we should go with Silverlight over the Flash and other technologies already available:

1. Support of .NET framework - if you are already .NET developer it is easy to start programming on Silverlight.
2. Support of Managed code - you can write programming in your favorite language which .NET CLR supports like C#,VB.NET, Dynamic languages (IronPython, IronRuby).
3. Better development tools -Visual Studio 2010, Expression Blend.
4. Large community- available lot of learning resource as compare to Flash technology.
5. Integration with Enterprise based technologies like WPF, LINQ etc.

How Silverlight would change the Web

1. Highest Quality Video Experience : prepare to see some of the best quality videos you have seen in your life, all embedded in highly graphical websites. The same research and technology that was used for VC-1, the codec that powers BluRay and HD DVD, is used by Microsoft today with its streaming media technologies.
2. Cross-Platform, Cross-Browser : Finally build web applications that work on any browser, and on any operating system. At release, Silverlight will work with Mac as well as Windows! The Mono project has also already promised support for Linux!.
3. Developers and Graphic Designers can play together : Developers familiar with Visual Studio, Microsoft.net will be able to develop amazing Silverlight applications very quickly, and they will work on Mac's and Windows. Developers will finally be able to strictly focus on the back end of the application core, while leaving the visuals to the Graphic Design team using the power of XAML.
4. Cheaper : Silverlight is now the most inexpensive way to stream video files over the internet at the best quality possible. Licensing is dead simple, all you need is IIS in Windows Server, and you’re done.
5. Support for 3rd Party Languages : Using the power of the new Dynamic Language Runtime, developers will now be able to use Ruby, Python, and EcmaScript! This means a Ruby developer can develop Silverlight applications, and leverage the .net Framework
6. Cross-Platform, Cross-Browser Remote Debugging : If you are in the need to debug an application running on a Mac, no problem! You can now set breakpoints, step into/over code, have immediate windows, and all that other good stuff that Visual Studio provides.
7. The best development environment on the planet : Visual Studio is an award winning development platform! As it continues to constantly evolve, so will Silverlight!
8. Silverlight offers copy protection : Have you noticed how easy it is to download YouTube videos to your computer, and save them for later viewing ? Silverlight will finally have the features enabling content providers complete control over their rich media content! Streaming television, new indie broadcast stations, all will now be possible!
9. Extreme Speed : There is a dramatic improvement in speed for AJAX-enabled websites that begin to use Silverlight, leveraging the Microsoft .net framework