I worked a lot with Qt C++ before QML came out. So I can say the mechanism is very similar between the systems, and a transition is quite simple for you.
Even though I built one QML app (almost 10 years ago), I am not sure if the generated code can be easily bridged to JUCE.
A big benefit of JUCE is it takes care of the thread safety between audio and GUI thread. I think in either way, Qt or QML you will have to do some work that takes a bit more experience.
My 2 pennies, if you can avoid mixing the systems, I would definitely do it.
I meant Qt entirely.
Even though I miss some features of Qt, they don’t make up for the hassle gluing the systems together IMHO.
Things like the QtDesigner (there are alternatives meanwhile though, and I don’t mean the Projucer GuiEditor), printing support, the plugin loader for your own plugin formats.
So sometimes I have to use third party libs for features, that were built-in in Qt, so that would be a reason to try mixing Qt and JUCE.
But those things are probably not so much QML related anyway.
So take it as my preference, but there is nothing wrong with going Qt anyway.
Maybe you can outline what you are trying to build, so people can give a more specific advise?