Difference between iOS 4.0 and iOS 4.0.1 on iPhone 4 Signal

CNET has done a test on the receipt of two iPhone 4, an updated firmware to iOS 4.0.1 and the other with the first iOS 4.0.

The test was conducted in San Francisco in three different categories of areas:
one with good reception (5 marks), the other receiving media (3 marks) with the last receipt of 0.
Although the test was carried out on AT & T network
What emerged from the test?
What places of maximum reception, the two iPhones on display show the same number of notches (the top panel refers to the iPhone 4 update )

In places where reception is average, however, the iPhone 4 is not updated shows usually 1-2 notches more:

The most interesting thing, though, is that in areas with poor reception, such as garage and basement, with the iPhone 4 on iOS 4.0.1 has always shown at least a notch more than the device:

In practical tests the two phones have behaved in the same way: same call quality. Even where the iPhone 4 on iOS 4.0.1 showed a notch and the other no signal, in both cases it was impossible to call.