Hey Doodle, just for discussion. I find it interesting in this discussion of the differences between DP and BS, they both have something in common, or, someone. Dio. Via Rainbow for DP and of course his relationship with BS over the decades after Ozzy, he elevated both Ritchie and Tony without overshadowing either. Heaven and Hell was a powerful album, and I feel was when you could start calling BS heavy metal. His influence on BS is further verified in his band Dio with Vivian Campbell. Scorching, intelligent metal.
Good observation.