If economy class, I would choose KE over CX. I would only choose CX only on business class or even first class.

I have to say, CX long-haul economy class is not too well in my opinion. The only good thing is about their wide variety of movies and TV shows in IFE. Though, the meal, seat and service is much worse than KE in my opinion.

My friends travelled on KE previously, and they like the meal, especially the famous bibimbap. It's the traditional Korean style of meal, and it is even provided on KE economy class!

And as far as I know, KE provide a 10.6" screen while CX just 9" if you care about this a lot.

KE seat pitch is also at least 1 or 2 inches larger than what CX provides.

And yea, I don't know if this suits you or not, but to me, I never like staying on an economy seat for more than 10 hours. I feel very tired and bored without any exercise. Therefore, I would surely choose KE as both legs via ICN won't take me a long flight journey, whereas CX's HKG/ORD takes you 15 hours (and you only have 2 meals in between, you will be pretty hungry I'm 90% sure, as the 2 meals are separated by around 10 hours)