SL does not require video codec to run industry standard videos like .WMV
But Flash requires video codec to run .WMV videos. Flash has also limitation to play other video file.
SL supports Scalable full screen video.
Flash does not support Scalable full screen video.
SL supports the WPF animation model, which is time based instead of frame based.
The animation model is frame based in Flash.
SL lets you embed true type font information directly into your projects, and download that information with the downloader object.
Dealing with fonts is fairly complex with flash.
SL does not support GIF, BMP format. It supports only JPG and PNG file format.
Flash support all image formats.
In SL the XAML is declarative while.
ActionScript is an imperative language, which brings itself the pitfalls of imperative languages.
Per pixel bitmap editing, bitmap filters & effects (drop shadow, blur, and glow) cannot be done in SL.
Can be done in Flash.
Silverlight uses XAML which is text based and can be output using a simple XML object.
Flash stores its shapes using binary shape records. In order to write shape definitions, you will need to either license a 3rd party Flash file format SDK.
Developer can use JavaScript as well as managed code VB.Net, C# for Silverlight development.
Only Action Script can be used as programming tool in Flash.
Using Silverlight Streaming, you can build a total video content site using Silverlight at no cost. The future for this service looks good.
Because of the Silverlight Streaming service, the existing Video Content sites might be moving to Silverlight site.No such free streaming service is available in Flash server.