The doctor of philosophy is one of the oldest degrees and in psychology is based on a scientist-practitioner model, where the candidate focuses her time on science and research.
The doctor of psychology, created in the 1960s, is a professional degree in psychology and prepares candidates with the practitioner-scholar model, with less emphasis in research training.
If you're seeking to teach at a university, a Ph.D. will be considered before a Psy.D., and the Ph.D. will prepare you for research and practicing therapy. Because of the intensive research background. A Psy.D., however, will prepare you for clinical employment, such as school counseling or work in a mental hospital.
More universities still offer the Ph.D. program than the Psy.D. (only about 30 Psy.D. programs are approved by the American Psychology Association as of August 2009), and it typically takes one to two years longer; both degrees require some internship as part of the program.
Psy.D. programs accept approximately 40 percent of the graduate applications, whereas Ph.D. programs accept about 15 percent. There are more opportunities for fellowships and assistantships, however, in the traditional Ph.D. programs.
As of 2009, all states accept both the Ph.D. and the Psy.D. to practice psychology.