Study the differences between Japanese and Chinese culture. Relate your business strategy to these cultures. How do your feelings and lifestyle relate to these cultures? Study the unique government system of both China and Japan. That will be important in business dealings. Do you have any Japanese or Chinese friends? Consult them. Ultimately, it is your choice. Do some research. Search the business languages of the world. Do more research, and you will find that Mandurin Chinese and the most spoken language in the world. This might be a deciding factor for you. What do you want to sell? Is that needed more in a Japan or China? What values do your products appeal? How do these products relate to these two unique cultures? Would you feel more comfortable in China or Japan? Study security in these two places. Are you wanting to travel for business, or mail your products. There are many more questions and factors to evaluate, but I think this is it for now.