Here, the 7970 ref fan at 47% is already more louder. As in my own experience, anything above 40% on AMD ref fan is loud, at >50% its jet engine annoying. The gtx670 fan up to 50% is quiet, but it ramps up really quickly from 55% to become loud.. seems like some sort of CFM threshold through the intake gaps. Either way I'm a happy camper, under load, benchmarks and games the fan speed stay around 45%.
While I don't disagree that NV's reference blowers are superior to AMD's, for me to maintain similar temperatures on the 4890 and 6950 I needed to set the fan speed at only 35-38% and on the GTX470 I had to crank it to 65-75%. Therefore, the fan speeds are not directly comparable. You do not need to have the reference design blower on AMD cards to work at 47-50% to maintain reasonable temperatures. You can just set up a custom fan curve in MSI AB and cap the AMD's blower at 38%.
Regardless, because HD7950/7970 cards are excellent overclockers, from the very beginning it was generally advised to go with after-market coolers for them as their reference cooler+blower fan design are terrible for overclocking.
I have to agree with others on the cooler for the 670 you have linked - it's junky. The 670 uses less power than a 7970. Put that 670 heatsink on the 7970 and the card would overheat in no time at only 35% fan speed, while 7970 works just fine at 35%.
Your comparison of the 670 to the 7950 PCS+ isn't apples-to-apples. Your 7950 is heavily overclocked to 1.2ghz while 670 is slower. What would happen if you overclocked your 670 to 1230-1260mhz? Isn't that a proper comparison? Max OC 670 vs. Max OC 7950 to assess the quality of their coolers?
The best reference coolers on the NV cards are on Titan/780 and 690. Compared to those the 670's cooler is budget/low rent. I agree that AMD needs to redesign their blower though.