In HK, the apple's product is tax-free, but many apple stores here in KM will not provide your warranty.For there are only 5 places in mainland of China will give you warranty for sure— that are the offical Apple Stores in Beijing, Shanghai...
In my opinion, Just get one here!
MBP is like 500~1500 yuan(varies from models) cheaper in HK(without tax), but if you buy one in mainland of CN, you get an extra one year global warranty, because according to the new rules of the services from Apple, all iPads, MPBs, MPAs, iMacs get 2 years garantee in PRC. So that is one more year goos stuff than any other couintries.
Plus, when you buying things in HK, you need to pass the government check when going back to the mainland, if you caught not paying tax bring new eletronics, you will be fined with extra.