Silverlight vs. Flash: The Developer Story - Jesse Ezell Blog

Silverlight supports the WPF animation model, which is not only time based instead of frame based, but lets you define the start and end conditions and it will figure out how to get there for you. No need to deal with matrixes. No need to calculate positions on various frames. It just works.

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Silverlight uses XAML. XAML is text based and can be output using a simple XML object. No need to buy special libraries to write files. No need to write your own libraries.

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Flash supports multiple video formats. The latest codec is really high quality and the bandwidth usage is nice.

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Compare that to the Silverlight story. Silverlight implements industry standard VC-1 codec for video, as well as offering support for WMV and WMA. Just about everyone already has Windows Movie Maker, but if they don’t it’s not a big deal. Why? Because Microsoft makes available a free Encoder SDK for producing WMA and WMV. So, not only are you using formats that people are more likely to be able to encode themselves, but Microsoft also provides your product with SDKs if you want to do the encoding yourself.

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There is no development environment out there for creating real desktop applications which is based on ActionScript. If you go the Flash route, this means that all your classes and objects have to be written twice.

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Functionality wise, there isn't much that Flash can do that Silverlight can't. I don't think Silverlight has support for alpha channels on video or low level, socket based communication at this time. Those eliminate a few specific usage scenarios (I know some people interested in gaming are really pushing for socket communication). The big difference IMO is that Silverlight targets application developers from the ground up, where Flash has a legacy of supporting animation. Flash is very much frame and movie clip oriented, which can be a pain when you are trying to do anything other than create a little animation sequence. Defining an application as a series of movie clips and frames is just lame.

Flex and Apollo are interesting. Apollo is a whole different ballgame though... it's like Central 2.0, and Central 1.0 was a complete failure, so I'm not expecting much from 2.0. It also doesn't deal with the creation of content, which is the side of the equation I am interested.

Flex, on the other hand, looks a lot more like Silverlight and does allow you to create SWFs. It is very much about application development. However, it still inherits all the limitations of the Flash file format. Although it has an improved animation model and can generate SWFs, you sill have the video / audio codec issues, the fact that you can only use actionscript, and the fact that you can't use your existing skills or tools. It also requires a  Java application server. So if you wanted to create an app that uses it to generate SWF, it's not a lightweight component you can bundle with your application. If an open source .NET port came out as a result of their recent announcements, it would be a lot more compelling, but that remains to be seen.

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