Originally Posted by linenhiker
For background, I'm a Korean-American who moved to HK recently.
I think, according to your criteria, HK wins.
Nightlife: HK has better nightlife. Gay nightlife does exist in Seoul, but much of it (and much of the foreigner-friendly nightlife in general) is in Itaewon, which has lots of U.S. military and so not the best vibe. Although sometimes that can be interesting, too (somehow the image of a black soldier and a white soldier making out on the dance floor of one of these bars is very memorable). Going out in Seoul is fun, but I think an outsider (someone with no local showing them around, etc.) would have more fun in HK.
English: Obviously, HK hands down. Not that many Koreans speak English, though obviously the younger folks do. Everyone in HK speaks at least some English.
Size of expat population: Is more expats a plus? If so, HK again.
Local cuisine: HK has been somewhat of a disappointment for us cuisine-wise. Of course, HK has a better spread of int'l cuisine, but Korean food is more interesting and varied than Cantonese food, especially if you're adventurous.
Costs: I believe Seoul is somewhat cheaper, though not by much at current exchange rates.
Exotic cultural stuff: I'm afraid neither place is very exotic. But after Singapore, Los Angeles feels exotic! Hong Kong has surprisingly old/atmospheric neighborhoods, and Chinese temples and such. But Seoul has its palaces, and you're probably more familiar with Chinese culture than Korean, so the latter may feel more exotic to you.
I think HK can probably be enjoyed by more people in a shorter period of time (b/c more tourists, more English, more easy things to enjoy). I think both places are way more interesting and fun than Singapore.
Thanks mate!
Singapore isn't much of a choice as I've to visit my parents, who work there, at least once or twice a year. I guess HK is the way to go then.