The clones that bind to a particular epitope with greater strength are more likely to be selected for further proliferation in the germinal centers of the follicles in various lymphoid tissues like the lymph nodes. This is not unlike natural selection:  clones are selected for their fitness to attack the epitopes (strength of binding) on the encountered pathogen.
What makes the analogy even stronger is that the B lymphocytes have to compete with each other for signals that promote their survival in the germinal centers.