The developer had 160 hours to develop the user interface for each framework, and with the resulting demos running on a Raspberry Pi 3 board with Raspbian, it was found that the Qt/QML implementation delivered a more responsive and functional user interface compared to the HTML5 version which tended to lag, and lacked support for touchscreen and a software keyboard by default. The developer also reported that the testing and debugging process was easier with Qt. The two demos are shown side-by-side in the video below.
It may look like an advertisement for Qt, but Sequality was allegedly not paid by Qt to develop and showcase both demos showing a clear advantage for Qt/QML. You can always try to find flaws in their experiment, as they report more details in a 10-page whitepaper (contact details + email required), where they also mention that HTML5 may have more styling features than Qt.