Did a lot of precision auto's years ago, spent hours playing with airspeed and rotor rpm, mostly UH-1/AH-1 airframes. My conclusions were that maintaining the rotor rpm in the 100% range throughout the flare resulted in more effective and controlled deceleration and touchdown, allowing the rotor to build to the high green (or limits) resulted in a less effective decel (with respect to rate of descent) that was not offset by the increased RPM for cushion. Disclaimer: this is just one person's experience in a highly unscientific test. Some might call it a "sample of one". YMMV