Kudos for testing this subject again. Testing will hugely be dependent on the kind of music/track u r using. Classical music does not stress MP3 encoder much. Try distorted/unlinear heavy guitar music. U might notice difference.Conclusion:
I hate all three tracks now and never want to listen to them again. lol
My go to test track is "Hush" by Deep Purple with its beginning "drummer" section played on guitar.