Definitely HKG both for location as well as because you would be flying CX, which IMO is the best among the OW Asian carriers, although as many pointed out you are looking at 3/4+ hours flight to get to south east Asia from HKG.
As per low cost, I personally do not fly low cost in Europe and I would never dare flying low cost in Asia but that's a personal (and unpopular) safety rule I give myself.