Did China Southern First Class from CAN - LAX (-777) a couple years ago. While it was no Cathay, it was decent. I'd compare it more to business class with one of the other carriers. It was a big seat that reclined probably 140 degrees or so, they fed us a couple meals that were ok, and I drank as much free beer as they would give me.

Never had a bad experience with Asiana, but on a long leg like yours it may be worth going with China Southern for the bigger seat.

Look at it this way: either carrier you go with will be taking you away from DEL so that alone is a great thing