When I create new Windows Phone project I have an option to create a \"Windows Phone\" or \"Windows Phone Silverlight\" app. I know that they have different runtimes and dif
Windows RT Xaml is quite new and People have to generate some knowledge first.
Silverlight for phone has been around for years and there's a load of tools available: Phone Toolkit, diverse Controls, etc. Just killing it off would have hurt many developers who built up intellectual property over a long time forcing them to start over.
When starting a project with Silverlight you will have more things around that help you get stuff done.
When starting with WinRT Xaml, you will have better performance, but will have to figure a lot out by yourself.
So the Silverlight option is there to not throw of Silverlight developers.
I recently started a new project on WinRT Xaml and my experience was that I had to recreate a lot of common tools like Caches, etc. But also a lot of things that were in Toolkits previously are now part of the platform itself. Also, when moving over to Windows 8, you get to share a lot of code which is nice.