EDIT: Please refer to @TheBootroo for a better answer
Although my answer was accepted by the OP, I want to revise (or even) remove my answer.
My answer was based on personal experiences with respect to Qt 5.2 in 2013 some of which is no longer valid today:
- QML is Qt Meta Language or Qt Modelling Language is a user interface markup language.
- QtQuick (both QtQuick 1.x and QtQuick 2.x) uses QML as a declarative language for designing user interface–centric applications.
Back at Qt 5.2 when you built a Qt Quick Application a significant question was whether the app was QtQuick 1.x or a QtQuick 2.x. Not only did this affect the components that were available, but, it altered how the application was rendered.
Back in 2013:
QtQuick 1.x applications was often chosen if you had to target older operating systems (e.g. Windows XP) or older hardware (e.g. OLPC) because the QML UI components such as Buttons were rendered by components native to your OS. However, this meant you were targeting a lowest common denominator set of UI components and that your UI experience may vary from platform to platform.
QtQuick 2.x application was chosen for a more consistent cross platform look, but, it required that your platform implemented OpenGLES sufficiently else, your application may fail to load. This, unfortunately, restricted your application to only the newest computer and devices that implemented OpenGLES.
When I wrote my original answer, this lead me to recommend QtQuick 1.x in some scenarios over QtQuick 2.x.
However, since then, Qt 5+ now allows you to target ANGLE on Windows which brings high performance OpenGL compatibility to Windows desktops by translating calls to Direct3D, which has much better driver support.