http://www.osnews.com/story.php?news_id=12981
Conclusion for those who don't want to read: aac is garbage for now.
Gabriel (5 years in Lame developing) wrote: MPEG natural audio standards (like mp3 or aac) are only defining the bitstream and the decoding, but not the encoding.It means that different encoders can encode in a different way, with different efficiencies.
It is like books authors and language. MP3 is using an old language, and some encoders are making good use of this language, as if an author was able to produce a very nice book.Now, you have a new language (aac) which allows you to express more subtle variations of concepts and wording. You know it is more powerfull, but book authors do not know it enough yet to be able to produce better books than with the old mp3 language.However, you know that when they will learn more and practice more the new language, they will be able to produce better results than with the previsou one.
This is just a simple transposition of things, but things are similar with mp3 and aac. AAC is more prowerfull and more efficient in theory. But the results are quite dependant of how the encoder is using the standard.
BTW, I am quite sure that AAC at 128kbps could be way better than mp3. It just needs a few more time.
link: http://www.hydrogenaudio.org/forums/lofiversion/index.php/t22521.html