The number 1 thing in China, if that is what you want to do, is does the combination of airline and agency have the ability to successfully recruit and get you through the process to get online. The best ones have a very low success rate from interview to passing a line check. The bad ones. - you don't want to know. Chose a worthless agency like Smile or Unic and they will probably screw up some small detail and you won't make it for some idiotic reason. in China you are probably going to get only 1 shot.
After that? Well we are all different with different priorities. Some want every last dime, some want lifestyle, etc. Some are more "culturally sensitive" than others.
Choose carefully and good luck.