Xiaomi Mi 4 Specs

There is only one word, BEST!
Why, because there is no benefit of excellent SoCs or features if your smartphone cannot survive for long. This phone has all you need!
The only potent rival is iPhone 6 because other Android skins lag too much and previous iPhones were way too small, and 6S series has force touch.
Rating 10, because the phone itself is so amazing, mentioning cons are not much of an issue.

After 6 months of using it I have to say that it is so far the best phone I've every had. Bought it for around 330 euro. Sill 6 months after can't find anything better than Xiaomi Mi4. The camera could be a bit better and SD slot would be a great thing to have.

Good screen, almost 100% sRGB coverage, sligtly higher red and green. Primitive tuning of gamma (3 fixed values only).
High screen to body ratio.
Good battery and battery life.
Good button ergonomics, small screen mode available.
Very functional and pretty UI. Some non-english services are in the phone firmware.
Easy root - in dev. firmware by default. Dual partition design for easy firmware revert.
Lots of storage in64Gb version. Sightly slower storage than newest Samsung UFS implementation but way faster than any class 10 microsd card.
Average sound pipeline (expecially inferior compared to bigger brothers with Sabre DAC and TI amp).
Some users report bad (quiet) mic or phone dynamic. No such issues on my phone yet.
Lots of models with different radios, hard to discern them. As a short guideline, in "about phone - model name" you should see either Mi 4W (3G WCDMA, no LTE) or Mi 4LTE-CU (3G WCDMA, 4G FDD-LTE - band1, band3).
Do not buy Mi 4LTE-CMCC and any other models, 3G and 4G in it will work only in China.