I certainly would not keep my savings in HKD. 3% no thanks.
1) RMB for the currency appreciation (no brainer)
2) your home currency becuase it is just that - and GBP, NZD, AUD all offer good rates - nationwide intl in the UK offer 6.6% and is fairly "safe"
Just dont leave it in HKD or USD since the currency appreciation is far from guaranteed meanwhile the rate is pitiful.