Psychiatric nurse practitioner or Psychiatrist

What's the difference? I wanted to know because my insurance company just scheduled me an appointment with a Psychiatric nurse practitioner instead of a psychiatrist.  So I looked it up in wikipedia :-).  
A nurse practitioner must obtain at least six to ten years of post-secondary education and then complete 600 clinical hours.

A psychiatrist must do at least 8 years then they must practice as a psychiatric resident for another four years.

The odd thing is they can both diagnose and prescribe.  I know most nurses in other practices cannot do that.  I don't see much difference between the two, especially if the nurse practitioner attends 8 years of school as well.  

If anyone knows different please comment.  Thanks.