mp3 is often better, it removes close frequencies that your ears can't hear baring tricks like very slow phase shifts. Speakers and amps are asked to do less work, so they often sound better, particularly at high volume. The same applies to the air the sound travels through and your ear drum and bio-pickups. You can often tell the difference, but its arguable if before or after mp3 processing is and improvement or destructive in terms of psychoacoustics. I often see djs who swear by wavs without knowing how the pitch and tempo adjust algo work in the equipment they are using. I.e. Top of the range pioneer Cdj decks run Busybox Linux and ffmpeg