"Millions of people convert their CD collections to a compressed digital audio format, often without considering the format or settings they use. With several different popular formats and lots of quality settings, many users just pick an application they like and use whatever the default settings are. ExtremeTech readers -- generally a bit more hands-on and do-it-yourself -- are more likely to seek out other applications or players and encode their audio exactly how they want.
Certainly a top consideration should be compatibility. We all have different audio devices, and it doesn't matter how good your music sounds if it won't play on your hardware. We'll leave that decision up to you; you know what software and devices you have and what they're capable of playing. Encoding time is another possible consideration, but honestly, modern computers encode audio so quickly that the difference in speed between one format and another is practically a non-issue."
This is one of the best, most hard-core looks at audio codec quality that I've seen. If you've been wondering about what audio format to use for your portable music player (whether it be an iPod, Pocket PC, or Smartphone), this article is a good substitution for doing all the testing yourself. I won't ruin the article for you, but let's just say that I wasn't surprised by the final result - I made the switch myself about a year ago, and have been very pleased with the results. It's also greatly simplified my ripping/encoding process, saving me time, which is a good thing.
Ultimately, however, it's important to realize that the best codec for me might not be the best one for you - it depends on factors such as speakers, headphones, music type, and the most important one: your ears. Check out the article - it's a great read!