@OP My advise is.... Try to pick cheaper school and see whether you will be happy there.
Okay, I will share my personal story with you. I grew up in Virginia and went to University of Virginia for my undergrad. UVA in our state is a big deal and people will respect you for going there. Because of this, when I was looking for dental schools, I also had to see their names and their reputation in the region. This is one of main reasons why I declined VCU acceptance because their undergraduate reputation is horrible in VA. In my opinion, you will be a dentist at the end, so you should go to dental school where you will be happy. (only if money is not a big issue). I also believe you will be a competent dentist as long as YOU try your best.
I currently decided to go to USC over a couple dental schools. I understand many people look for different things, but I wanted to go to school where it has its brand, great sports teams, great campus, hot girls, things to do, etc. Therefore, I find USC and UVA being very similar in many ways. Plus, since money wasn't an issue (HPSP) and I wanted to be happy and have fun while becoming a dentist, I chose USC.
As OmnipoDent stated, Tufts is a great dental school and I personally think their program is better than many dental schools out there, but it's not a big deal in Boston, because there are Harvard and MIT right next to it. However, I personally think Tufts's dental school is better than BU and Harvard. It's really sad people in Boston don't realize it.
I don't know too much of SIU because I didn't apply there.
Again, this is my personal opinion, so it could be different from what you are looking for.
pm me if you have any more question. Good luck with your decision and please let us know! I know what you are going through!