What is the preferred solution to start new projects - are both actively developed? I don't see too many commits on qtscxml and documentation is also not great, no graphical editor etc. ...
The module itself is a tech preview so it means that it's there for public testing.
As for the graphical editor, I don't know the roadmap of the module. AFAIK, its current goal is to make it easy to integrate scxml into your application.