I hope you are enjoying Suzhou. I have gone there a lot on business over the last few years and have found it to be a pleasant city.
I think the key question for me would be what class of service do you normally purchase? When you said "discounted premium", did you mean discounted business class or discounted first? If so, I think you have a lot of options and should choose a carrier based on how you personally prioritize schedule versus hard product (e.g. lie-flat beds) versus soft product versus accumulating miles for future use.
If you are flying economy, I would probably stay with UA for the chance of being able to use upgrades to business class.
For me, I buy business and stick with UA (at least so far) because schedule and the certainty of lie-flat beds trumps everything else.