I don't know any specifics about BU b/c I never applied there, but I think it's affiliation with BU and its history are probably its greatest assets. I've noticed most patients don't know anything about dental school, so they rely on the reputation of the greater university on which to base their opinions. For example, I go to USC, and despite everyone on SDN thinking it's a crap school, every patient I have seen has told me they thought it was the best in the country (obviously, they don't know Harvard has a d-school!) My point is, the name and reputation count for a lot.
Also, affiliation with a large university means lots of $$$ and research, which provide more opportunities (and look really good if you're interested in specializing.) And as for specializing, BU has a ton of programs...if you want to get into a specialty, your best bet is to go to a school that has the program you want and get your foot in the door that way. All the people I know at SC in ortho and OS (ie, the toughest specialties) graduated from SC and spent the majority of their time hanging out in those departments, chumming it up with the faculty and what not (along with studying their asses of for Part 1s).
Finally, BU has a long history, which means lots of alumni and good connections when you get out and are looking for a job. At SC, the alumni are really big on volunteering also at the school, so there are always a lot of old guys hanging around with tons of knowledge and experience to share from their many, many years in practice.
Anyway, like I said, I don't know a whole lot of specifics about the school, but that's what I've picked up through the years in general about dental schools. Hope that gives you a starting off point at least for those essays. Good luck!
Wow.. I did more SDN searched about BU. There is a whole lot of BU bashing and it's not just from one person. Darn. I don't know what to write on my supplemental.