Thank you !
I would prefer XAML over HTML5 as it provides flexibility, performance and again that is in accordance with my experience. Jerry Nixon from Microsoft has a few good reasons supporting this - blog.jerrynixon.com/2012/05/windows-8-why-i-choose-xaml-metro-over.html
I personally prefer XAML over HTML.. And that's true with most .NET developers. Microsoft internal dev teams spent a long creating and optimising html / winjs. While it cant match xaml and c# performance isn't so bad.
I'd advice to do what you are comfortable with.
Hi, I prefer HTML5/JS the support and community is bigger, hence, the information on web is more complete
The benefit I see with html5 is that you can easily port it with many platforms.
Whilst I cannot say I am a fan of the HTML5/JS programming combo, I do believe it lends a degree to the ease of use for the developer and an aspect of portability to their finished apps; now, with that said, let it be known that the XAML/C# pair are far superior when it comes to programming power and flexibility. They were designed from white paper to functional language to be the brick and mortar of modern Microsoft platform applications, both hosted and local. I do suppose HTML5/JS is suitable for simpler tasks and easier to learn; however XAML/C# is probably the winner of the fight for heavy lifting and overall platform superiority.