Bottom line is that beggars can't be choosers. Many countries have to take Sinovac and with the number of people that already have been vaccinated, it's obvious that there are no serious short term issues in terms of safety. The efficacy is currently the biggest issue of Sinovac compared with others but it does appear to prevent serious issues in virtually all cases so it's fair enough to have it in circulation. As mentioned, there are far more than health decisions at play and in the real world, that's how it is.
There are still many things that have yet to be determined like the length and the extent of the protection as time goes on and how each vaccine will fare against present and future variants. There has been promising results with Pfizer but it'll be at least another year before the picture starts to be clearer. Anyone looking for certainty is living in the wrong world and in Hong Kong we have the luxury of choice and the situation doesn't warrant any urgency in making that choice.