Next purchase--Beauty Dish or Soft Box?

I have two Profoto lights now with white umbrellas. My next purchase will probably be either a beauty dish or softbox. I take occasion freebe portraits for friends or local schools so I do not do this for a living but would like to improve my results.
Profoto is now offering a $50 rebate on their $373 beauty dish.

For those of you who have used both, which would be the next logical step in equipment purchases- the dish or softbox?