This article pursues two objectives. The first one is to analyze the existing theoretical evidence on the alleged superiority of the strategy of diversification over the strategy of specialization for business results, as well as the superiority of related diversification over non-related diversification, which has been the subject of abundant analyses in the literature specialized on the topic. The second objective is to compare and contrast the above proposals in order to contribute empirical evidence regarding such assumptions. A comparison and contrast of 846 Spanish industrial companies were made using the Survey on Business Strategies (ESEE is the Spanish acronym) for the 1991 - 2002 period. In addition, an index was built to enable identifying the corporate strategies that those firms have. More specifically, a disaggregated analysis was made first by corporate strategy and afterwards by industrial sector. Using panel data, the study results show that there are significant differences based on the type of corporate strategy and on the type of industrial sector analyzed. Those results open the door to a potent line of research.