You need to note that the power levels are only approximate readings of the power level of different APs and solely determined by the card and the driver that you use. You can in other words not compare the output between different cards or drivers with each other in any way.
When you say that the power levels using one card are more accurate than using another it is therefore completely irrelevant. It may very well be that a PWR reading of 40 using one card equals 90 using another. Again only use this output to compare the signal strength of one AP with another AP using the same card and driver.



