When comparing these file types, do use something other than the pc sound system.
I have difficulty descerning anything noteable using only the Altec 2.1 pc audio ... I do percieve diffs piping the sound into my main stereo.
I do find still greater diffs using FLAC vs. Apple lossless too... and this might be due to the media player or codec (s) being used. FLAC having simply more resolution and detail which offers greater presence. AIF is quite close though... and actually a near toss up.... again, I'm thinking it's the decoders and encoders being used.
In fact the Lame mp3 encoder I feel is better than the AAC format at the same bit rates. yet again, another encoder/decoder algorithim.