I had just superficial experience with each of these tools, which I think is more adequate to answer your question since VB and Delphi are very productive for p

I had just superficial experience with each of these tools, which I think is more adequate to answer your question since VB and Delphi are very productive for people who have little experience. QT and Qt Creator is more evolved than both (I don't know recent Delphi versions, but still think so). In Delphi (not sure about VB) you can do Text1.Caption := "Hello World". In QT Creator (last time I tried), you have to create some code to connect the signals to slots and still call a method to achieve the same thing. It was a bit more work but, easy, clear intuitive, well documented and has advantages when implementing more advanced features in a more generic way. I'd choose QT over both others today even for beginners and even disregarding licenses.