Price is not a concern. Which should I buy?
Good about ASUS:
Out of the box 120Hz
GSync
Good about Korean monitor:
90Hz~144Hz
PLS Screen
If you are a competitive FPS gamer, you might prefer the ASUS unit.
IPS panels are a good middle ground for everything; design and gaming. I personally prefer IPS, but I am content with 60Hz. It depends on your uses.
Though, some Korean models are very overclockable, there's no guarantee that you will get favourable results.
They always get 90+ Hz. Sometimes 120Hz. Rarely 144Hz.
Also, you could damage the panel during overclocking. It's up to you if you wish to accept any of the listed trade-offs.
Can you provide a source for panel damage during overclocking? I've never heard of an indecent, but I would assume it is possible.
I shouldn't have used the word damage. I've been considering the capability of my own 1440p monitor to go above 60Hz, so I had done a little reading, lately. Some people have stated that you can damage a monitor, but I haven't found any evidence.
Rather, you can get artifacting or a failed overclock, as you might expect. Other problems like burn-in image retention. That's what I found most people would complain about following a monitor overclock.
Every monitor is going to have different overclocking capabilities. And honestly, I wouldn't expect all Korean models to go above 90. Most appear to reach 75-80. A guaranteed 120Hz would be worthwhile, if you're a competitive FPS player.
Also consider Overlord monitors. They sell 1440p monitors pre-clocked to 120Hz, I believe.