So, I'm planning a DONE4 and have a similar dilemma to the OP, so I'll tack it on to this thread:
Basically, I can put together an itinerary with CX flying the Europe->Asia leg, but as a result I'll end up stuck in one of ICN, NRT or PVG overnight. Alternatively, I could fly on the AY nonstop to ICN and save the overnight.
Having never flown either CX or AY, I'm left to wonder: is CX's business class product sufficiently better that it's worth an extra overnight to choose it versus AY?