Here at ch9 they were using silverlight variable data rate steaming before it worked correctly and talked about being on the cutting edge, but there isn't a reason to do that here. enogh said (by me)
conclusion: HTML5 may someday replace SL video, but not yet.
will HTML5 video be ready before the plug-inless metro IE10?
Will HTML5 support variable data rates?
Dose it seem to you that the HTML5 file is large for the small display were warching?