Nord used to be where the prostitutes were located. Maybe still are.
Midi is better than before but still an area of offices and where tramps gather. One of the ugliest areas of Bruxelles imo. Some nice kebab houses though.
Central is the place to be. I usually recommend Novotel de la tour noire. People like it (never slept there myself I live 30 min from there).

You can see the prostitutes in Nord from the train, when you arrive from the north. They seem to do good business, even early in the morning when I passed there recently.

mokena44 --

You were exiting Centraal, I'm pretty sure.