It's an apples/oranges comparison. If someone was gonna bother with distinctions, obviously Brooklyn's entire southern area was mob heavy (except for the housing projects in Coney, Marlboro, Canarsie, etc.). An entire was family (Colombos) was, and still is, centrally based there.

Both Brooklyn and Bronx are probably neck and neck in the attrition race. I would bet that. Russians, Jamaicans, Chinese, and now even hipsters are starting to take southern part of Brooklyn. (the hipsters already took carroll gardens and east williamsburg).

I love borough history and demographics, which is why I respond. www.forgotten-ny.com for a trove of brooklyn/bronx info.