I think the answer to that depends which option is more valuable to you. In other words, which currency do you currently need more?
It's really difficult to compare the two options, as the exchange rate of HHonors points to SkyMiles is 10:1.
If you're worried about the recent devaluation of HHonors points, and your daily hotel rate is high enough, the 50% Diamond bonus on base points could help you add to your HHonors balance.