They are both displaying the same information to you in a different way. So they are both correct.
A nice analysis on the signal fix is here:
http://www.anandtech.com/show/3821/iphone-4-redux-analyzing-apples-ios-41-signal-fix
it's the hardware.
it's the hardware.
seem here
my Dad's iPhone 3GS has 4-5 bars
My iPhone 4 only has 1-3 bars
they are both in the same room and next to each other
Both are running iOS 4.0