I think there are two advantages: 1. Reviewing other papers in your field is a critical thinking process that may provide new insights about your own work. 2. In the United States, at least, performing peer review is considered to be "service to profession" and therefore can be part of a promotion portfolio. When you complete and submit your review, the journal should send you an email acknowledging your work, which serves as your documentation. I would also say that I have been successful with several journal publications of my own, so when I perform peer review, I think of myself in a mentoring role. This may not be a direct benefit, but I see peer review as helping other scholars to succeed, so it does make me feel good.
I think there are two advantages: 1. Reviewing other papers in your field is a critical thinking process that may provide new insights about your own work. 2. In the United States, at least, performing peer review is considered to be "service to profession" and therefore can be part of a promotion portfolio. When you complete and submit your review, the journal should send you an email acknowledging your work, which serves as your documentation. I would also say that I have been successful with several journal publications of my own, so when I perform peer review, I think of myself in a mentoring role. This may not be a direct benefit, but I see peer review as helping other scholars to succeed, so it does make me feel good.