I've flown both, including AF on the 777 CDG-HKG. KE wins hands down. The middle-of-the-night arrival at ICN kinda sucks, but I'd sooner have that than 2-3-2 in J on AF's 777.

ICN-HKG is a pretty short flight. I wouldn't worry too much about the seating on that.

What's the difference in terms of price and mileage earned? Or mileage to be paid?