Mike writes how flash sucks. And he is right.
The Adobe Flash Player is a multimedia application created by Macromedia (now a division of Adobe Systems). Flash Player features support for both vector and raster graphics, along with a scripting language and bidirectional streaming of video and audio content. The player is a virtual machine that runs Flash files, which are often embedded in websites to present animations, games, GUIs, or other visual interestingness. If you?re reading this website, you probably know all of this. What you might not know is that Flash sucks. It is the bane of the Internet, and it needs to go away.
Silverlight from Microsoft sucks much less. Why? Because it doesn’t get compiled before hand which means you can make much more of it search engine friendly, but also it interacts with HTML, DHTML, and AJAX so done right you can build silverlight pages that only use media functions when you are doing media rather than all of the time.