AIFF vs AAC
AIFF (Audio Interchange File Format) and AAC (Advanced Audio Coding) are two coding algorithms that are used mostly by Apple products, although the latter was not developed by Apple. These codecs dictate how the audio is digitized and recorded in digital format. The main difference between the two is in the manner with which the encoding is done. AIFF is a lossless format, which means that all audio information is kept in the file and nothing is lost. No matter how many times you encode the file between lossless formats, the quality of the sound would remain the same. On the other hand, AAC uses a lossy compression algorithm that discards the least important data. Converting between a lossy and either a lossy or lossless codec would always result in degraded quality. The more you do it, the worse it gets.
Since AIFF is lossy and uncompressed, files encoded in this format is much bigger than lossy and/or compressed audio by roughly 10 times. Using AIFF means you need to have a huge hard drive, which can be quite a problem when portable media players have a very limited drive space. Aside from taking up too much space, using AIFF can also drain your battery quicker as the hard drive needs to spin longer in order to read the entire file. For these reasons, you would rarely see AIFF utilized in music players. The only feasible application of AIFF is in mixing or editing audio as it preserves sound quality very well.
AAC is very popular, more so when Apple decided to use it as the default file format for their iPods and their music store. AAC also offers significant improvements when compared to the very popular MP3. In contrast, the very old AIFF is rarely used, if at all. There are lossless codecs that utilize compression to reduce the file size significantly without compromising quality. The only advantage of having your file uncompressed is that the processor need not decompress the file. This has been made insignificant because of the current computer technologies that make short work of such menial tasks.
Summary:
1. AIFF is a lossless audio codec while AAC uses a lossy compression algorithm
2. AIFF files are much larger compared to AAC files
3. AIFF is better suited for audio editing while AAC is better suited for personal listening
4. AIFF is hardly ever used while AAC is a very popular codec