I've said that their implementations are different and that they serve different purposes.
Windows Universal apps could run on Android, same way Android ART is being ported to Chrome. But it seems as though Microsoft has decided to stick to their own OSes, so how could they be truly "Universal"? That is the main criticism between developers.
Microsoft is making it easier to get into their ecosystem, but is only being unidirectional. If Microsoft had a runtime that was truly universal, that worked across all mobile OSes, don't you think developers would swallow the red pill?
I guarantee you all: In a few years, Google Play will compete directly with the Windows Store on Windows x86_64 devices. And yes, apps can be resized. WinRT assumes touch, vs Android that separates these HIDs, just another consideration.
Microsoft is the first to bring their platforms together with a Universal App Runtime, but they were not the first to develop one. That was the point I was trying to get across, but it seems like I have created an Android vs Windows flame fest.
P.S: WinRT will make Windows (Home/Student/possibly even enterprise) the OS for "small children and computer illiterates" smh. The day Win32 dies is the day I develop for Apple.