Having recently flown on them, I'd highly recommend CX as well.

Even CX Y is going to be better than Delta Y. The domestic carriers just do not have the same level of service as asian carriers. I'd definitely try to avoid Delta (although I suspect DL's reasonable redemptions are less available than CX anyways).

Oh, and as for Korean on the A380. Haven't tried Korean but I was on a Qantas A380 in coach. The exit row seat was pretty much tolerable for the trip. Work had sent me LAX-SYD in coach. I "liked" the A380 coach so much that on the way back i went ahead and spent my own miles to redeem a QF F award on the A380. Any flight over 8 hours should be in Biz if you can swing it. But, if Y is all you can do, the A380 isn't a bad way to do it. And I've read Korean has greater pitch than other carriers (I could be wrong here, just from their ads)