"Jim H" wrote in message
news
Not much in it.

Without an ABX (which I know you wouldn't care about anyway)
difficult to tell the difference.
Treble clearer on the 2s(?)


I obtained a MP3 plug-in for Winamp and used it to perform the conversion of
both Mp3 and Mp4 files to .wav files. I then checked them out for time and
level matching in Adobe Audition, and found them to be good. I then spent
several hours PCABXing, and frustrated myself with a lot of "random
guessing" type scores, even though at times I felt I was reliably hearing a
difference.

Since the MP4 (AAC) format has received a lot of favorable press, and some
of this music seems like the kind of stuff that makes some MP3 encoders do
bad things, I think the time was well-spent.

I conclude that MP4 does not have a day-and-night advantage over MP3. Thanks
Keith, for the stimulus to actually do the comparison.