why this model receive better rating than the GL551JM when they are the same laptop except the gpu?

The SSD slot peeking through the opening is a half-sized mSATA, same as in the Asus N551. Asus uses it for the caching SSD (8 GB) in both models. The G/GL551 is basically a repainted clone of it (same as G/GL550 was a clone of N550) - surprised that's not mentioned at all. Pathetic that since 2 years Asus still refuses to equip their mid-range multimedia and gaming laptops with at least a full sized mSATA or better, M.2, but insists on retaining the space-wasting optical drive and even downgraded the chassis to an ugly half-plastic one instead of all-metal.

4710HQ is correct

Nope, I disagree about speakers. While it might be true that laptop sound is a matter of personal taste, but here, Asus has drastically downgraded the sound system from previous iterations. Sound is sharp, low volume, high pitched, and little mids.......bass, well it is non existent even though the notebook size allows for a much larger resonance chamber.