Was it the upgraded hardware (from G1 to Legend) or software (from Android 1.6 to 2.1):
And now that the old phone was promoted from "crash testing" to experimenting with the latest and greatest of home brew rom's, an experiment is in order:
HTC G1, flying Android 1.6
HTC G1, flying Android 2.1
HTC Legend, flying Android 2.1
The conclusion we can get from this is that the newer version of Android doesn't have any added noise reduction filters and that it is indeed the hardware that is better in the newer HTC Legend.