There is world of difference regarding seating comfort between F and Business on the JFK-ICN route. KE flies Premium F on these routes, fka Morning Calm Class, which recline 180 degrees. KE's C seats still lag far behind SQ, JL, NH, and even American carriers in recline, pitch and leg support. I would go with Premium F.

When I fly long haul in KE C, I'll have a few Remy XOs after dinner and sleep like a baby.