I feel that Silverlight and Flash will continue to coexist for a long, long time because of the simple fact that they are really made for different types of developers. I can't imagine designers ever preferring Microsoft's toolset and I can't imaging programmers coming from other languages being satisfied with developing exclusively in ActionScript.
“What’s better – Flash or Silverlight?” Enough people have asked me that I felt I should post my opinion on the question.
Designers will prefer Flash. Programmers will prefer Silverlight. There. I said it.
Having used both tools I can still confidently say that Microsoft’s design tools and design workflow are still generations behind the sophistication of Adobe’s tools. Adobe has had a better track record of satisfying the needs of the design community for more than a decade. A Flash workflow with Photoshop, Illustrator, Flash and Flex Builder is still far easier, more powerful and flexible for designing user interfaces than Microsoft Expression Studio. Expression Design has the capabilities Illustrator and Photoshop had four generations ago. Expression Blend has nice integration into the development workflow (though Adobe CS3 finally has similar integration) but Expression Design is not, and probably will never be, the powerhouse Photoshop is.
All this said, I feel that Silverlight and Flash will continue to coexist for a long, long time because of the simple fact that they are really made for different types of developers. I can’t imagine designers ever preferring Microsoft’s toolset and I can’t imaging programmers coming from other languages being satisfied with developing exclusively in Actionscript. As for me, being both a designer and a developer, I intend to master both.