The U.L.N.A (Ultra-Low-Noise Adaptor) is a power cable that has a resister in line with the fan, cutting the amount of power that the fans uses, which slows it down. If you use those, there is not a way to speed up the fan without powering it down and removing it. They also have the noise damping pins (vibration compensators) you can use if they fit in your case, it didn't fit mine.
Now letís take a look at the 80mm fan. Both fans have the same number of blades and you can see the curve change in the 80mm version a little better than the 120mm.
A closer look at the 80mm fan, before we place it in an acrylic case
The 80mm Fan specs are different as it comes with two different noise adaptors.
L.N.A and U.L.N.A are different resisters lowering the power the fan gets and in turn makes the fan quieter. I placed the 80mm fan at the top of my acrylic case to push the hot air from the case out of the top of the case.
Over all of the Noctua fans have taken the spot light in my acrylic case I picked up a couple years ago on clearance. The two 120mm fans are working in the temporary case the kids use for playing games. The fans are working great and keeping things cool in both cases.
A fan controller is still a better option if you want to control the speed on-the-fly and without a power down. The two colors on the fan and shell makes them a little more noticeable and if you really wanted a different color, it would be easier to change with some dye.
Sound level is under 20dB (A) for full speed on both fans. First look you think they are moving more air with the rating of the NF-S12 at 81 m^3/h which equals about 47 CFM which is starting to get on the low side.
Thanks to Noctua for sending over these samples!