Great insights and detailed comparison. Having used both, I like that you highlighted the strengths of both and where using each would make sense. It is not which is better but which library is suitable to your needs.

I think that the frameworks were created for the reason that they encompassed best practices. I find that they are highly usable and should be used as much as possible. Of course you still need to understand the concepts of Responsive Web Design to style the page elements and structure the layout based on various screen sizes. Using these frameworks allows us to have best practiced code in our app.