Tianjin is desperately short on 320 captains. The flying there on the bus is excellent. Their pay is currently below other contracts and Tianjin isn't one of the better places to live. Overall I think it is a good gig especially since they are offering a 3 week off option for only a slight penalty in pay. The flying is very efficient so u will still get 80 hours per month.
CS? I don't know and based on their below average pay I would bet they r having a tough time recruiting 320 guys. They have a large 320 fleet. Expats as always will fly what the locals don't want to fly. I would guess the flying for expats will be very poor. In China poor flying really blows. Maybe fly 1.5, sit in hotel 10 hours, fly back. I have stayed in several CS hotels and they r dumps, beyond anything most pilots have ever stayed at in their careers outside of China. The only thing I know would be a positive is Guangzhou is the base. I lived there for a year and it is a decent place for expats.
If I were going to choose between the two I would choose Tianjin mostly because CS is a big unknown. In China u need to choose very carefully as you will only get one shot, and only with one airline.
Good luck.