Puzzled by 4.7 speakers being way louder than 5.5. Anyone?

So I stumbled upon this (Russian) video today, in which the reviewer compares the 4.7 and 5.5 speakers. To my surprise the 4.7 speakers sound way louder and possibly better. To me this doesn't make sense and leads me to believe something isn't right with the 5.5.

Did any of you compare both the devices speakers and what were the results?

The video: (speech can be translated into English)

https://www.youtube.com/watch?v=AKLex3CNATM&t=2m35s