AAC stands for Advanced Audio Coding, which is an audio format used to store sound into digital folders that can be replayed on digital audio players. The Apple company created Apple Lossless, which is used in iPods, and Apple Lossless uses bigger files. The difference in size can be about ten times as much and is very important in mobile devices where capacity is often an issue.
The price you pay for Apple Lossless becomes less of a dilemma for users, as the sound quality of Apple Lossless is flawless. The AAC files are encoded with very high bit rates, or very big like low bit rate AAC files. However, it would be best if you come up with the proper equipment for it.
For example, you should not be using sub-standard headphones when utilizing the Apple Lossless. Apple Lossless is a free of charge audio format, and Licensing fees are also different. However, AAC is not free, and the fees can vary depending upon which units are utilized. AAC is better for mobile devices because of it’s admirable size to quality ratio.