Q: Can you tell me the advantages of using the AAC format compared to using MP3? If AAC is better for clarity or what not, can I convert my whole library in a few simple steps? What’s involved in making that happen?
A: AAC is said to offer better quality than MP3 at the same bit rate. That said, if you already have a lot of music in MP3 format, it’s not worth changing it. First, if you convert your music from MP3 to AAC, you’ll probably lose quality; at best, the music will sound as it did in MP3 format; at worst, the fact that iTunes has to decompress then recompress the music will make it sound worse.
You can certainly re-import your CDs to AAC format if you wish, and replace your MP3 files. For most purposes, AAC files at 160 kbps sound excellent; about as good as 192 kbps MP3 files. This means you save a bit of space using lower bit rate files.
However, if you think you might ever want to listen to your music on a non-Apple music player, don’t convert your music to AAC. Very few music players other than the iPod currently support AAC, though this may change in the future.