about properties

[jajdoo]

this might be a silly question, but still..
taking the following example from the qt docs:

class MyClass : public QObject
 {
     Q_OBJECT
     Q_PROPERTY(Priority priority READ priority WRITE setPriority NOTIFY priorityChanged)
     Q_ENUMS(Priority)
 
 public:
     MyClass(QObject *parent = 0);
     ~MyClass();
 
     enum Priority { High, Low, VeryHigh, VeryLow };
 
     void setPriority(Priority priority)
     {
         m_priority = priority;
         emit priorityChanged(priority);
     }
     Priority priority() const
     { return m_priority; }
 
 signals:
     void priorityChanged(Priority);
 
 private:
     Priority m_priority;
 };

class MyClass : public QObject
 {
     Q_OBJECT
     Q_PROPERTY(Priority priority READ priority WRITE setPriority NOTIFY priorityChanged)
     Q_ENUMS(Priority)

 public:
     MyClass(QObject *parent = 0);
     ~MyClass();

     enum Priority { High, Low, VeryHigh, VeryLow };

     void setPriority(Priority priority)
     {
         m_priority = priority;
         emit priorityChanged(priority);
     }
     Priority priority() const
     { return m_priority; }

 signals:
     void priorityChanged(Priority);

 private:
     Priority m_priority;
 };

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I'm having some trouble understanding this: if the property is not dynamic, declared as a class member and i am responsible for emitting its signals and writing the methods it uses, who am i declaring Q_PROPERTY for? what are the advantages of predefined properties over dynamic ones?