Well, I can tell you this much; there are none. The best GPR program for you, is the one you like best. I know I am probably not helping you much, but if you think of it, it all makes good sense.
Here is what I would advise you to consider in your quest for that elusive "best GPR" program:
-What kind of supervision the residents are under
-Hospital cases (what kind - IV, OR, full mouth, medically/physically compromised)
-Implants
-Trauma
-OMF emphasis (ER, 3rds, Trauma)
-Advanced endo and/or perio training and exposure
First and foremost, talk to the residents ... they hold your answers.