I am still studying, but as i heard from my lecturers, the disadvantages of China are that the country herself is still an economy in transition, their law system is not as standardize and mature as HK, reputation is not a good one also (corruption).
But due to my research, foreign direct investment (FDI) is growing really really quick with this 10 years, almost 80% of the world's top 500 companies invested in China.
Sure there are less risk to invest in HK, besides the cost maybe higher.