from Seattle- Beijing, my personal preference is Hainan Air, an Airbus A330. Comfortable, great service. A 'no- brainer' choice. A couple years back, Hainan received a 5Star rating; also, you are allowed 2 50lb bags for stowage.
Delta came on board recently. Delta has been aggressive in acquiring gates in China & London. They fly 767's, okay, but the thing is their service sucks, the food sucks. My wife refuses to fly Delta now. I see China Southern has partnered with Delta on the Seattle Beijing leg. Delta allows only 1 bag, 50lb, on their Beijing flight. I was quoted an additional stowed bag (last Dec9) would be an additional $75.
Kind of funny, I see Emirates flies Seattle- Beijing going East..Dubai, then Beijing, the 1st leg via a 777. +14hrs just Seattle- Dubai and a 16 hour layover before boarding for Beijing (+7hrs). That would be fun in a different way if you are in no hurry. An additional $300. Not bad considering going the other way from the US West coast.
I use Orbitz, play with the +or- 3 day feature. Delta pricing aggressiveness has made the other airlines pricing competitive. You just have to play with Orbitz a few times a day, a few times a week. The deals are there. It is patience & good luck since the price structures constantly change a week, 2 weeks, or so before the flight. You have to pull the trigger very fast when the better price presents. It does not last for long. You can view the seating charts of all the flights on Orbitz and make an educated guess from that.
My personal choice of airplanes. 777-300. Best ever for comfort. Floor beams are composite fab.
My personal choice of air carriers, Seattle- Beijing, is Hainan. Always outstanding service and comfort. Jet lag is nill. Go figure.
When the situation occurred, I flew other Asian flagged airlines...always great service but that way does not present a direct flight to Beijing. I try never to fly an American flagged airline. (Piss poor. Routine maintenance is wanting complicating comfort issues. Food sucks. Offstandish service). Has always been that way for me.