I have two different xfx 270Xs:
The older "ghost thermal" runs about 38-42C at idle with a fan speed of 20% (800rpm)
The newer "black edition" runs about 35-38C at idle with a fan speed of 20% (1500rpm).
The "black edition" fans are 10mm larger, but the minimal idle speed it set much higher for some reason. Its upsetting because its very noisy compared to the older version which was basically silent at idle. I have a support ticket in now to see if there is a fix.
Its funny because the 20% doesn't even scale right on the new cards:
------- 20% 50% 100%
Ghost 800 2500 4500
Black 1500 2000 3600
The bigger fans are definitely better at load, at 100% they are able to drive card temps down into the 40s. At 60% temps are in the upper 50s which is cooler and quieter than the small fans could ever hope for.
Can someone else confirm the black edition fans at 1500rpm @20%?