CA's 330s offer more space, but I don't think it is a major difference over the 777s and 748. I'd go by schedule and flexibility, and in your case, unless you don't mind taking bus from SZX, i'd pick via PEK because it has more flights to HKG comparing to CTU. I just flew CA from JFK to TYO via PEK in J and paid under $2300, a great value. There is an immigration checkpoint for connecting passengers and the line was long in the morning, on the way back during midday, there was no line. So it depends on time of day. The flight itself was fine, seat was comfortable, I slept well, flight attendant was friendly, food and entertainment is mediocre at best.