[sonitus mirus]

 
This is like the effect of testing 2 different colognes at the same time. After a while both smell the same.  Some how the brain refuses to catch differences but there are big differences.
The compressed file sound thin, bright, no separation, no space, instruments sound smaller, no real bass and after a while of listening one gets a headache or ear pain.  I hate digital recordings anyways. I'm an analog purist when it comes to listen to music seriously. Still I listen to FLAC or MP3 @ 320kb on my computer when working.

 
Your description and experience with compressed files seems to be more of an extreme exception rather than a normal experience.  Not even sure how it would be possible to get such a drastic difference in sound with a 320 kbps mp3 unless there was some major issue with the encoding method.  I'm glad I don't have similar issues, it would be miserable to me.

 

[ProtegeManiac]

   
Your description and experience with compressed files seems to be more of an extreme exception rather than a normal experience.  Not even sure how it would be possible to get such a drastic difference in sound with a 320 kbps mp3 unless there was some major issue with the encoding method.  I'm glad I don't have similar issues, it would be miserable to me.

 

From my experience 320kbps barely affects imaging, and in fact it only really affects the tone of some percussions and the bass guitar. The treble roll off is next to inaudible since many speakers and most (dynamic driver) headphones tend to roll off past 12khz anyway (which is also why when we listen to a planar or electrostat with a flatter response all the way to 20khz we're so amazed by its treble), and if you get a frequency response of most recordings, most of them don't use instruments that have significant response in that range.