I'm a big map enthusiast, and always searching for the best offline maps available. As of currently, in 2016, the best offline map for China (and most Asia in fact) is definitely HERE Maps (formerly known as Nokia Maps).

I have both Android and Microsoft mobile. Unfortunately Google is not supporting Chinese maps due to the dispute with Chinese authorities, so the Android version is great for all other countries except China. Microsoft version, however, is by far the best offline mapping software in the market right now. It's in its own league compare to, e.g. maps.me. Even better than all the commercial alternatives I have tried. over the years.

I usually compare OFFLINE version of Here maps to the ONLINE version of Google maps. Until today, it's difficult to say which is better? Both have incredible accuracy, for even the smallest off-road routes. Having said that, Google maps is definitely more pleasing for the eyes (although I think this is because downloadable offline maps don't want to too graphical on the expense of larger file-size).