Both of Hu and Cai returned home to teach in prestigious universities and start their careers in home after "attaining" a non-existent Ph.D. degree from likewise prestigious schools abroad.  This is the similarity between Hu and Cai.

Reputedly, Hu made up a retroactive thesis ten years later and got the bona fide doctoral degree from Columbia.  But up to date there has not any official announcement made by LSE that Wonky Cai did acquire the degree from the school in mid 80s.  This is the difference between two of them.

Certainly, we cannot exclude the possibility that someday when Cai steps down as the "president" she might get back to the school and finish her thesis and have her degree awarded.  Ha!