Let's say you're invited for interview for both schools, and because of scheduling, you can only attend one interview. Which one would you choose, and why?
On the other hand If I had not recieved any acceptances as of now, I would do everything possible to attend both interviews. No sense in wasting opportunities!
Think about where you'd see yourself. If NJ is close to home, then LA is far, far away.
USC is astronomically expensive too. I've been told that it's the most expensive dental school in the country. Compare that to the UMDNJ tuition. At the UMDNJ interview, we were told that you should have no trouble getting NJ residency by your first day in school, but confirm that with the Financial Aid Office. So you're paying state tuition for four years. Sweet deal.
As well, USC has some pros. If you think you'd really benefit from PBL and only PBL, then USC is the way to go.
IMO: If there's a scheduling conflict, call the Admin Office and beg to have it changed. They're very understanding if you've got a legit reason. I'd go to both because you can't change your mind about interviewing after you've turned them down.