Think about spending the extra money for Business Class...It's like a $100 add-on from a discounted fare--I think I paid about $200 in July. There is ZERO legroom in Y on Chinese planes...The on-the-ground service is much better than a US-domestic flight in F or C...You get lounge access (usually with decent food/drinks), there's a 'cheat line' for security, and I find the bags come out a heck of a lot faster too. The intangibles alone make it worth it.

I'd go with Air China. I don't have a good track history with Shanghai airlines. Plus, Air China runs some 777s and 747s on the SHA-PEK route--I had a nice seat on a nice plane in an EMPTY C-class cabin recently.