Trip to Hanoi questions

Ok, so I really loved this but it really made me have some questions. Is Susan Sontag more believable because she writes in journal entries and in the first person? Is this "more real" writing of any more importance than fiction? Is her angle to gain support through the rhetorical use of journal entries or did it just happen that her journal entries seem to be more convincing than a fictional story? Or is the fact that she discusses points of view that aren't spoken of often the reason it sounds so convincing?