Global ROM vs. Chinese ROM MIUI differences
1. The Global ROM is made for international users. But still you can use the Chinese ROM sane as Global. Some installed apps on the Chinese ROM will be useless for you using outside China.
2. For using the Chinese ROM same as Global, you need install Google apps (play market, account). As for the Global ROM, it has built-in Google apps so the users does not need to download the Google installer.
3. Global ROM has Google Play Store while the Chinese ROM has its own different app store that offers as much as variety of apps the Google Play Store offers.
4. Xiaomi is a Chinese product as well as the MIUI skin. It's an advantage for the Chinese ROM since it gets the updates first before the Global ROM gets it.
5. Chinese ROM has the option of font style setting while the Global ROM don't have that option.
6. The Chinese ROM keyboard has issues but you can have it fixed by downloading other keyboards from the Google Play Store.
7. The Chinese ROM has also a built-in feature to ROOT the device.
Overall, the Global ROM and Chinese ROM has its own unique features made for its target market. The two may have difference but the other one does not mean it is more capable and better than the other.