I tried both the NH-D14 and the Phanteks PH-TC14PE and cooling was very similar, but more importantly the Phanteks sounded quieter or smoother, something I put down to having two identical size fans out of the box.
I see the NH-D15 comes with two of the same fan so that may resolve that issue without an expensive fan swap. However I don't think that's enough for me to overlook the colour issue!
I always hear this about the fan noise with the noctua and phanteks will be interesting to find out how the NH-D15 sounds if its that annoying whoosh or just a calm sound!