I had the same decision as you a couple years ago between Harvard, UOP, and a couple other schools. I chose HSDM for several reasons:
-Although UoP is a great school, Harvard is more prestigious (if that's something important to you)
-It's actually cheaper to go to Harvard than UOP
-You honestly don't know much about dentistry until you actually go to dental school so don't swear off specialization before you start (keep your options open)
-A class of 40 vs a class 150
-The faculty are AMAZING!
-The students are awesome and you get to know everyone
-Many more research opportunities in the dental and medical field
-Saving one year didn't seem to justify closing the door to specialization
Come to Harvard!