whenever you have people from different ethnic groups, values, religion, or affluence, there will be talk of separation.
Personally, I think it is better to allow for some form of self government when these situation arise. However, pride often gets in the way and some are reluctant to change the status quo.
Economically, it's better to have control over territory particularly when resources are involved. The argument for having large entities is always the same whether it's countries our business. It comes down to power and influence. That was part of the idea behind forming the EU to counteract the growing north american influence.
It's interesting to read some of the negative comment on China. They may have a repressive system and lots more work to do with freeing markets and the press but they certainly don't have a history of sticking their nose in other people's business as the US loves to do...