The service on those airlines is about the same. Bigger equipment is usually better, though (avoid the 737s/727s if possible). Pricing should also be about the same. No point in booking on elong/ctrip as you should be able to secure the same or better pricing in Beijing.

Domestic F/J is nothing special, but Y can be pretty miserable and the fare difference on that route should be quite small. I usually u/g myself on China domestic legs to seperate myself from the riff-raff in Y.