As from March 2013, Microsoft allows Adobe Flash content to play by default on its immersive Internet Explorer 10: http://redmondmag.com/articles/2013/03/11/new-ie-10-flash-policy.aspx
When asked about Silverlight, Microsoft says
Silverlight will not be supported in immersive Internet Explorer 10 since these capabilities are superseded by the new WinRT API.
Does this mean that there are capabilities of Adobe Flash not present in the WinRT API that forced Microsoft to allow Flash? What are these capabilities?
This decision to support Flash in the touch version of IE10 really had more to do with continuing to allow legacy Flash sites to run during the majority of the Web’s transition to HTML5. WinRT API and HTML5/CSS3/JS do contain all of the core capabilities like rich, hardware accelerated animations, audio, and video, and is the superior platform to use, but MS understands that there are some folks who aren’t quite there yet, so their older Flash apps still need to be viewable in the meantime.
Short Answer: This decision to allow Flash in IE10 has more to do with backwards compatibility than Flash or Silverlight being a better option than HTML5 or the WinRT platform for apps.
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