http://silverlight.net/forums/t/3015.aspx

A comparison of SilverLight 1.0 vs Flex/Flash

Some of the SilverLight limitations no longer apply in SilverLight 2.0 beta.

• Linux support is handled by Moonlight - sponsored by Microsoft via Novell
• SilverLight has data binding support
• SilverLight has control library
• SilverLight control library shipped with full testing tools - I assume these can be modified to do SilverLight unit testing
• Socket programming is possible now
• SilverLight has building download support.  Not sure about what upload support means, pushing a data into a web service?
• Disagree with performance being slower - I would argue that both system would run equally fast.  There's no reason one should be slower than the other.
• SilverLight is deployed in one XAP file.  The XAML is included so that it can be indexed.

The next link is a RIA test web site.

http://www.bubblemark.com/

On my machine (FireFox):

• DHTML: 60 fps
• Flex: 63 fps
• Flex (cached): 63 fps
• Java (Swing): 63 fps
• SilverLight (JavaScript): 56 fps
• SilverLight (CLR): a whooping 330 fps

You should free up some memory for your browser for the HTML/JavaScript tests - restarting the browser usually does the job.  If you already have 10 tabs open the DHTML/JavaScript ones won't run as well.

Seriously, you got to see this to believe it.