Benefits of taking postgraduate/PhD-level courses during Master's
While it might make a small difference, I doubt that you will get all that much benefit from the courses based on how they appear on your transcript, even if they are annotated with information about their level.  The simple reasons for this are that:


Courses cannot readily be compared from institution to institution, and
Even a high grade in a course doesn't really say anything about what you took away from it.


Instead, the main "resume" benefit you are likely to obtain from these courses is in their side-effects: higher-level graduate courses tend to give you opportunities that don't come in more stock courses, like doing significant projects (which sometimes even lead to publications!), giving class presentations, getting involved in research, getting to know faculty, etc.  

Those are where I would recommend looking for benefit, and why it's often better to take less classes but invest more deeply in each at the graduate level.