It doesn't make sense to compare different models when it comes to RPM. Their cooling design including fan blade & size is different. I had similar concern before. Their RMA guy told that the default idle setting of their fan speed is based on its noise level (25dBA)
OK but no manufacturer explains how the cooler is designed.
In their product description, no manufacturer gives, the min/max noise, the min/max fan speed, the min/max temperature, the speed curve used.
Before to buy my Gigabyte GTX650 "too cold", I had a Sapphire HD4850 "too hot".
For both, I've been obliged to use MSI-Afterburner in order to put an efficient fan curve.
I think it's not good to take the customer for a ride...