I'm not surprised to hear that the Boulez Lulu seems less compelling than the Böhm. It's a gross generality, but for all of Boulez's genius, the "general wisdom" used to be that his performances of other people's works were more analytical than inspired. They might very well be the most clinically precise study recordings for someone with their head buried in the score, but was the music better served by other conductors? On the other hand, he really was a conductor as well as a writer and composer. Like I said, a gross generality.