WUSTL. Even though both of programs can not guarantee you getting a job after graduation, at least people heard of the name "Washington" when you come back to China.
Most people in China do not know WUSTL is in st.louis. They only heard of the name "Washington". That's what matters. Once they heard the name Washington, they will probably think the school may be better than those who-knows-what-it-is schools in UK/US. Ranking means nothing to most HR in China. They most likely know nothing about it.
Simon has strong reputation in finance research. No doubts about it. In terms of PHD program, it can definitely compete with MIT, Harvard and Chicago. However, MSF and PHD are two complete different programs. If we talk about job placement for MSF students after graduation, I doubt Rochester is really that much better than WUSTL. I personally like WUSTL's curriculum better, it is very comprehensive which suits a wide range of career objectives.