close_event->accept() vs qApp->quit()

ravas

If we have a QMainWindow subclass with:

MainWindow::closeEvent(QCloseEvent* close_event)
{
     something ? close_event->accept() : close_event->ignore();
}

and a main function with

main ()
{
    ...
    int return_code = app.exec()
    qDebug() << return_code;
    return return_code;
}

the debug does not output anything;
however, it will if we use a different function with qApp->quit().

What does accepting the close event of a QMainWindow do differently than calling qApp->quit?