Hi Kevin. In my opinion, AAC is the best as it sounds better than MP3's and the files it creates are considerably smaller. AIFF files are uncompressed and are exact copies of what's on a CD so they will sound the absolute best but they're huge, at least ten times larger than AAC or MP3. Do what I did as an experiment. Take one song that has both loud and quiet passages, both high (violins, cymbals, etc.) frequency and (acoustic bass, electric bass, bass drum, organ bass pedals, etc.) and encode it in all four of the options offered by iTunes and see if you can tell a difference. Let your ears (not someone else's) be your guide. One additional note, if you're copying an already compressed format (say MP3) I wouldn't recommend converting it to another compressed format (AAC) as this could significantly degrade the quality. Good luck. John On Jan 3, 2004, at 11:10 PM, Kevin Willis wrote: > I just got my G4/400 about two weeks ago. I installed Jaguar on it > last night. It sure is beautiful. I have spent this evening playing > around with it and setting up my preferences. One question I have so > far...What are the different music formats in iTunes? There is AAC, > AIFF, and MP3. What are the differences? Is one better than the > other? Which should I use for ripping CD's? > > > Thanks, > > Kevin