Why Merlins sound better then Sonus Faber

Sounding "better" is completely subjective. Everyone has different ability, interpretation, and preferences of what sounds "best". So, if you think Merlin sounds better than SF, lucky you! You get to save 5x the amount of money. Go buy music with your savings!

more transparent, closer to the original recording without adding anything else

Unless you were there when the material was recorded, mixed, and mastered, and had a far better than average audio memory, or immediate access to both pairs of speakers, how would you know which is closest to the truth? Way too uncontrolled of a test to make accurate conclusions.