Temperature/Noise Ratio
On these perf/noise ratio graphs, we remind you that it is best to be placed as much as possible at the bottom left of the graph. For the reading, the left most point symbolizes the ventilation in 12V, the one in the center the ventilation in 8V and the right most in 5V.
At 65W, whether with one or two fans, the NH-D12L is “pulling at the heels” of the NH-U12A chromax.black. Even so, with this profile, running the fan at full speed is not the most profitable thing to do given the verticality of the curve in these conditions. 
At 95W, our heatsink of the day comes back to the NH-U12A, recording a very low difference in push and push/pull. Moreover, the addition of the second fan does not yet seem justified. Even at half speed, a single fan is more efficient than two at low speed! 
Finally, at 125W, we notice that the D12L and NH-U12A stand out from each other, whether they are with one or two fans. Moreover, we also notice that the gap widens with the DeepCool AS500 Plus and NH-D15 compared to the other power profiles.
The addition of a second fan allows the heatsink to regain its color and, above all, to hold up at low speeds. So in case of overclocking, adding a second fan may be a good idea.
