I received the replacement fan from Fractal, and did a comparison between the new fan and the Revoltech.
A quick word beforehand. This is obviously a completely un-scientific approach to things, which I know is not this forum's preferred method of testing, but it's the best I could do.
Some quick background information, just so you know where I'm coming from as far as fan noise: I received my Axe-Fx II in August, it's in a rack with with my poweramp and conditioner. The fan noise didn't really bother me until the last few weeks when it started getting very loud. However, it did always have a very annoying pitch to it that made it stand out, even above the sound of 8 radiator fans in the water cooled PC it's next to (the fans are actually very quiet, but 8 of them add up). I always found that a bit annoying, as the Axe doubles as my sound card (yeah, I lug the rack back and forth with me) and sometimes I found the pitch rather distracting.
I tested first by throwing a motherboard on my PC test bench, and then plugging the replacement fan and the Revoltech in to a fan controller. This allowed me to turn them on and off instantly, and turn one on after the other to see how much louder either one was than the other, instead of swapping them out in and out of the Axe and doing my best to accurately gauge the differences. I then also tested each fan in the Axe with the lid on. The original stock fan in my Axe was the Hui Tong, the replacement fan that Fractal sent me is a Top Motor DF126015BL, which is listed at a fan speed of of 4000rpm, a CFM of 16.00, and a Noise level of 29.60 dBA. The Revoltech specs are listed as 2500rpm, 12.31 CFM, and a noise level of 19.99 dBA.
The Revoltech is still far more quiet than the Fractal replacement fan. The Top Motor replacement fan though is quieter than the Hui Tong fan, and does not have the same annoying whine. The Top Motor when installed in the Axe II sounds pretty much the same as my Ultra fan if my memory serves me correctly.
For now I'm sticking with the Top Motor because I think a little noise is better than paying for two fried processors to be replaced. I'm not worried about the heat now, but in July and August, if playing somewhere with an ambient temperature in triple digits and a ton of humidity, I know I'd be worrying.
Of note if using the Revoltech fan: It is 60x60x20mm, as opposed to the 60x60x15mm of the Fractal fans. I was informed that there are two different fan screw sizes that Fractal uses: Approximately 1.29" and 1.49". If your unit has the smaller screws, you will need to remove the white spacers from the rubber standoffs, otherwise you will not have any room to put the bolts back on. I had the shorter screws and had to remove the spacers to test the Revoltech in the Axe. Other than that, no modifications are needed.