Philadelphia Orchestra music director Christoph Eschenbach, who has a passion for 20th-century music and is legendary for his fiery performances of Shostakovich, could not be much more different from the man he replaced, Wolfgang Sawallisch, a low-key European conductor of the old school, whose tastes ran more to German romantics. “So you have to wonder why [Eschenbach] has spent so much time in his first year and a half as music director of the Philadelphia Orchestra plowing through repertoire that was the specialty of his immediate predecessor. Comparisons are inevitable, and Eschenbach is not coming out on top.”