if the ratings thing is an issue i would go to BC. i am biased, though, since im going to be a 1L at BC next year. i also was trying to decide between the two schools so i know what you are going through.
after speaking to the dean at BC, my understanding of why BC took such a drop in the rankings is this: (1) BC lost two professors (one died and one retired) and therefore, for that one year, had a much higher than normal student-to-teacher ratio. those two proffs have since been replaced. (2) since most people from BC tend to work in boston or nyc, 9/11 had a much greater effect on BC's employment stats than on BU's. A lot of people who were offered jobs then had the offers rescinded. the last year that the employment stats were reported was from '01.
long story short: BC is expected to jump back up to the low 20s or high teens next year.
hope to see you at BC!