The Bold 9700 will work in regions with GSM service, however, in some areas of China, they only have CDMA and in this case, your best bet is the 8830. I don't know which specific areas have what though. Generally speaking though, most well populated areas of China supposedly have GSM capabilities, so the Bold 9700 should work fine in those places.
Now then, if you want to use SIM cards over there, you will need to unlock your Bold 9700. Most World Edition 8830s came GSM unlocked (so you could use a SIM card from anywhere), but the Bold 9700 is typically locked to a specific carrier. It isn't hard to get them unlocked though. Depending on who your carrier is, you may be able to get an unlock code from them, or you can purchase an unlock code from a 3rd party (if you'd like more info on this, send me a PM).
One other thing. If you unlock your phone and use a different SIM card, don't forget that your phone number is tied to the SIM card, not your phone, so you'll have a different phone number every time you change your SIM card. In addition, while I haven't tried it yet myself, you likely will not get BlackBerry data access. If the plan you get there includes data, you may be able to access the WAP browser, but you more than likely will not get the full BlackBerry service. That's because the phone has to access your BIS/BES account which is tied to the carrier you're on now. Now then, I could be wrong, or maybe you'll get lucky, but...
