It actually does not matter whether or not QT is better or worse, it does not even matter why wxWidgets was chosen in the first place. It does not matter whether you like it or not (as it happens, I really hate wxWidgets). All of this is completely irrelevant.
The one and only thing that matters is that the application is built on top on wxWidgets and the major part of code uses, depends on, or otherwise interacts with wxWidgets.
Using this particular toolkit is a decision that Yiannis took when starting the project, and it cannot be undone at this step of development (or at any later time).
Migrating to a different toolkit at the current stage (even if you could prove that it is 200 times better) would be outright crazy. It would not be very difficult, but it would mean to rewrite the whole application from scratch.