Penn undoubtedly has the name. It's a great dental school.
NYU has it's own pluses. The biggest is location. In terms of reputation, everyone knows that everyone knows NYU. NYU has a top 4 law school, a top ten business school, a great medical school and a world renowned film school.
Both schools are crazy expensive, though.
Ultimately, it's up to YOU to determine what school will fit you the best. Just because you pick a certain school does not guarantee you anything. Some people feel more comfortable and thrive in a less competitive environment. Others need to get pushed to be motivated. Others want the name and don't mind living in a bad area.
Put it this way: My friend attended a pretty bad medical school. Yet, he is currently a resident at a very, very prestigious hospital for a specialty everyone wants. He constantly reminds me that had he attended a top medical school, he probably wouldn't have matched into this program because of competition from his classmates. My two cents