METRO apps may be better as they get tested before they go on the store.
but WinRT != Metro
from what i was picking up one could write a C++ app that uses WinRT and it might be hiding whatever....
Metro apps that go to the app store get some testing.
IMHO MS should also offer app store apps that are non-metro but get as much checking as possible.
but even if the app is C# + .Net + Metro and gets tested they can not promise it will be 100% safe.
just that they check for well known issues and try to catch stuff.