The purpose of this study is to determine which is more beneficial to improving learner writing: reviewing peer texts or one's own text. The study took place over one semester at a Japanese university with 51 students enrolled in two writing classes at two proficiency levels. The students at the lower proficiency level reviewed peer texts, while those at the higher proficiency level reviewed their own texts. Multiple task sheets were used in both classes for students to give detailed feedback on texts. To examine gains in writing quality, a comparative analysis was conducted on writing samples collected at the beginning and the end of the semester. A questionnaire survey was also conducted to investigate the students' perceptions towards the tasks. The results of the analysis indicated that the students who focused on reviewing their own texts made more total gains in score than did the students who focused on reviewing peer texts. On the other hand, a significant correlation was observed between score gains and perceived effectiveness of the task with the students who focused on reviewing peer texts. The pedagogical implications of the results are discussed.