Sound quality is subjective, and so are the results you get from the many different audio compression formats. When you deal with competing lossy compression formats, however, many companies (and some individuals) will attempt to lead you to believe the opposite. They will try to convince you that sound quality has absolute values that can be equated with different formats, and with different bit-rates within the same format.
Encoders for the competing formats are implemented in different ways. Some lossy formats are more advanced than others and include features you can use to achieve better quality without increasing the bit-rate, but it’s misleading to claim that one format is better than another without providing more details (such as the specific encoder used and all the settings used to encode the files). It’s also misleading to imply that any bit-rate is equivalent to a certain quality level.
When you configure a program that creates MP3 files, you may see the term “CD-quality” next to a certain bit-rate—usually 128 or 160 kbps. This is misleading, to say the least. Microsoft and Sony have claimed that their proprietary formats sound “just as good as MP3” at half the bit-rate. While their respective ATRAC3 and WMA encoders can be more efficient than some MP3 encoders, it’s quite a stretch to say that ATRAC3 or WMA files encoded at 64 kbps will sound just as good as the same files encoded with MP3 at 128 kbps.
There are so many factors that affect ...