Can you compare the different types of biographical writing and their spiritual outcomes as described in the source?

The preface outlines a hierarchy of biographical writing as a form of service. Chapter 0 details that writing about worldly Gurus is a worldly service whose fruits are temporary and limited by time and space. A higher form is writing the biographies of many saints, which does yield spiritual fruits but is still considered partial or one-sided. The ultimate form of service, which can lead to salvation, is writing the biography of one's own Sadguru and then studying it with unwavering devotion through practices like Parayans and Saptahs.