I love China phones because they are affordable but can be very decent. However, there are some Android knockoffs plus even big companies *cough* Samsung *cough* who have been caught cheating Antutu's benchmark app to show scores that are much better than their performance.
One modification method is by outright manipulation of Antutu's tool itself to report higher specs. The other one, which they say was what Samsung use, is to temporarily boost performance if it senses that a benchmark is running. Lastly, another still fakes graphic performance. More info can be read here
I guess, this is why forums and blogs that are able to give info on how devices perform can be very helpful in giving people more idea on phones that they own or plan to buy.