In P515 VRM is more advanced than N1X : the should name it VRM2
From P515 manual : (Page 10)
This original VRM technology calculated the various states of the strings for each of the 88 notes of the keyboard from one instant to the next, and the timing and depth of the damper pedal presses. The enhanced VRM now also calculates and reproduces aliquot resonance in the upper octaves, and the full resonance of the soundboard, rim, and frame. This technology gives you vivid, bright, richly varied expression, effectively reproducing the complex acoustic interactions when performing on an actual piano.
they have added Aliquot Resonance and Body resonance in this VRM (2).
That's why i find that my N1X sound better with the Pianoteq 8 Side chain Resonance….. than VRM (1)…
So P515 CFX sound better than N1X CFX…