No, it's Qt Quick vs. QWidget. QWidget was created in the pre-mobile days, and while still very useful to make high-quality work horse desktop apps, the mobile platforms are much better served by Qt Quick in terms of theming, animation and touch support.

This fragmentation is frustrating sometimes, but in the end what counts is whether the framework has solutions to your problems, and it usually does. (Meanwhile, Qt Quick is improving on the desktop over time.)

This is why on an application I have done back in the 5.3 days, I decided to throw Qt away and rewrite it using standard C++ for the logic, with Java and C++/CX for the UI.

I was much more productive and I had much better integration with the respective OS APIs.