I really have to say it that it depends a lot on yourself.
I do not know much about BU, but this is what I can tell you about NOVA.
1. Nova is newer than BU so it has some advantages. The faculty doesn't seem so set in their ways that they do not listen to you. They really take student's concerns seriously, and you feel comfortable addressing your professors. For example, say you get all your syllabi, and you have 3 tests in a week- if you ask them, they will change it for you.
The faculty here are amazing. They really care about the students, and you really get to know them. They are willing to spend time with you to help you understand and learn techniques.
2. Nova is expensive- not sure if you are in state or out of state, but it is a lot to handle. However, there are some things to consider:
The tuition quote does include a $10,000 budget for a top of the line kit which you keep. It is seriously amazing, and you will use many of the pieces when you leave. You rent your supplies from other schools (not sure if this is the case at BU).
Also, things like parking, gym, etc are all included in the price.
3. The quality of life is very good here. This was a big one for me.
The students are happy here. Sometimes they are stressed, and work very hard, but for me, I was struck with the feeling that students like it here. I did not apply to BU, so I don't know how students seemed there.
Also, whenever you get stressed out- which will happen- dental school is hard- you can be at the beach in 10 minutes. It sounds stupid, but it has definitely helped me step back and relax.
You may not realize how much good weather affects your mood, your health, and your motivation, but for me it has huge implications. I get sick less often (yay for vitamin D!), I get out of bed quicker, and I am more ready to learn.
Finally, it is great to get advice from other people in the profession, but unless they are really involved with many dental schools, they probably don't really know. Things today have changed a lot since they were in school, and they will be continually changing when we start practicing.
Remember it is your life. Go where you think you, personally, will be able to learn dentistry the best!
Congrats on your acceptances!