I don't see why playing in a bigger stadium hands the advantage to China. They drew 0-0 in Shenzhen a few weeks back and that was played in a 60,000 seater.
I can see the atmosphere in either stadium verging on hostile, which is the way you want it for a big game regardless of the politics. You want the away team feeling uncomfortable. Massive difference if you can get 40,000 people yelling abuse and booing compared to a few thousand in my opinion.