I can most certainly hear the compression when compared with CD digital audio.
I fully understand the difference between data compression and dynamic range (not audio) compression.
What I'm saying is, lossy data compressed audio formats are already compromised enough to rule it out as a medium for audiophile use. Worrying about the dynamic range at that point is moot. It's going to be played on tiny, terrible sounding speakers.
with 256kbps AAC, really? yeah MP3 is old and even at 320kbps it throws away everything above 18kHz (which I can't hear personally, but some people can). However AAC is newer and better and blows MP3 out of the water (so do OGG and OPUS, btw). We got a lot better at psychoacoustics since MP3 started out. I strongly doubt you could hear it in a proper A/B test.
and the iTunes files are 256 kbps AACs, you can't hear the compression
remember that 'compression' in this context is data compression and not audio compression (which acts directly on the dynamic range of the source)