wav its the better coice if you want to have a better sound. mp3 sounds often a little crap for me. we older guys who have had vinyl in our youth hear them clicks and quietschs and zischhhhs anywhere we hear this compressed mp3-format, because its only the half of the original music: you hear only what your ear hear, not what yxour heart ;-) joke
but you can convert it easy to this format, there are a few free converter out there.
excuse me for the inconvenience, but i´m a little bit oldschool. and a bootlet naturally sounds not so good, so in wav it sounds at least good notsogood