Originally Posted by soulstudios
Agreed except that 99% of cases MP3 is better than AAC, if you use a decent encoder. AAC is "technically" a better specification, in reality though Apple's encoders are rubbish, and a lame-encoded mp3 is always better than an AAC file (you can turn off lowpass filtering for both).
There are no absolutes like that in lossy coding. Some audio causes problems in Lame's MP3 that are not there in Apple's AAC, and some are the other way round. You may well be right that MP3 generally
outperforms AAC despite having an inferior specification—I haven't done enough testing to know either way. Spotify using Ogg Vorbis doesn't sound bad, either.
Disabling low-pass filtering means that bits that would have been used to encode the (more important) mid-range frequencies are used to encode the (less important) HF frequencies (17k plus, or thereabouts). So the frequency response may "look better", but at the expense of accuracy in more easily audible parts of the spectrum. Developers have spent a long, long, time tweaking presets to make them as good as they can be for a given bit rate. Any (simple) tweak like that that any end-user can think of has probably been tried before many years ago.