First, business class on SQ, CX is fine and don't worry about losing your F status if you want to be efficient on time. Only long flight (4 hrs) is Sin/HK or Sin/Tpe.
Second - they are all good visits, depends what you want to do? Shop, culture, monger, what? Tell me more re what you like and I'll pm you with some suggestions....
FYI, i do almost every country in asia except japan 3 or 4 times are year for past 25 yrs, plus lived in 4 of them....so let me know what you're looking to do.