I'm a Delta DM and much prefer flying Korean Air. I take the Korean Air flight to ICN often and find their service to be a big step up from Delta. However, if you are flying business class, try to book the flights with lie flat seating as opposed to the older reclining seats. They have a chart posted on the KE website which shows what routes have this configuration. Its even worth it to make a stop - say LA - to get the lie-flats on the long segment.