...Between lossless and lossy audio codecs?
Back in 2010, all I listened to were mp3 files with a 320kbps bit rate. Soon after that I starting reading up on lossless sound quality from forums specializing in audio technology. What I got from it: FLAC is amazing, and you'll never look back.
for 2 whole years I was convinced that I could hear the difference between FLAC files and mp3/m4a. Just recently I switched to iTunes Plus m4a and couldn't be more satisfied. I honestly can't tell the difference. Can you?
Just to be clear, VERY (I mean very) few people can tell the difference. 90% of people who say they can are lying, and even with expensive sound equipment, differences are everything but distinct.