I don't think that your analogy is fair, but I agree with the point you're trying to make. Personally, I like the BB just because I can use more weight. More weight in a freeweight modality is a good combination. I think both are effective exercises, and there is no reason to exclude one or the other.
If making an exercise more unstable was the most effective way of going about things, then why not do everything on a stability ball or air pads? Sometimes overloading the agonists in the movement is more desireable, and sometimes forcing the stabilizers to handle a heavier load, as opposed to a load that is simply less stable, is more desireable.