It depends on how you plan to choose in the future. If you plan to find a Japanese company to work in the future, Peking University. If you plan to enter the civil service, Beijing Foreign Studies University. In fact, there are not many things to "learn" in the postgraduate stage, mainly to learn some research methods, do more independent research and write papers. The level of Japanese department is definitely higher than that of Beijing Foreign Studies University, and other software and hardware outside Japanese department are definitely better than that of Peking University. I don't know much about your situation, so decide for yourself ~ Come on ~ ~