Unless he is an egghead, he should pick hk.
Leading a top univ. of the 'most promising' country to excellence on par with Qinghua and Beida is much more satisfying than fighting for excellence in just one academic field.
Maybe more importantly, making contributions to his motherland in the bid to surpass America is much more rewarding than being just one among say 500 top scientists in the kingdom of science. A Chinese American scientist is just another person in America. Nobody gives you a damn unless you get a Nobel or a top spot in NASDAQ.
And, guess the pay and perks here is much better too.
Do you think one of the questions he would face getting of the plane is:
Are you a member of the Party?