To compare acupuncture with dry needling because they use the same tool is absurd.  I have had both modalities performed on me and they are in no way similar other than the mechanism of delivery.  Acupuncture is directed at energy flow and typically is a needle placed just below the skin- this is based on meridians and chi.  Dry needling is targeting a much deeper source.  It is not intended to block, enhance or do anything else to the bodies energy flow.  It is targeting muscle groups and is a very effective way to get the job done.  

I am not a physical therapist, I am a patient and can speak very strongly to the benefits of both practices.  I use acupuncture for anxiety and dry needling for the muscle issues that the anxiety causes.