Up to here, I have always talked about XAML versus HTML and about C# versus Javascript, comparing features and functionalities. Working in the HTML side of the story, there is another actor of which we have to be aware of. It is the CSS stylesheet that is automatically created, as a common point to contain user interface aspects that apply to the whole application.
It is a very common practice in HTML programming to set visual aspects of elements using a cascading style sheet and it is really important to centralize styles and make them much more maintainable.