Unlocked mobile phones - buy in China or elsewhere?

I will be traveling to China for work in a month's time - and I plan on being there for a long time, more than 2 years. I am wondering whether I should wait till I get to China to buy a mobile or should I do it from here. (Australia). Because I am hearing there could be problems if I am using a non-China region phone at various levels and it might be preferable to buy one in China. (I lost my smartphone a few weeks back and I have been using a much cheaper replacement for now). Also would it be a better deal if I sign a contract with a Chinese carrier? Thanks.