I’m a fan of the iTunes Store’s convenience, design, and integration with iTunes, but I am a bigger fan of the Amazon MP3 store’s cheaper prices and higher bit rate MP3s (all of which are fantastically DRM-free). Amazon isn’t known for their stellar interface design though, so finding things in the iTunes Store has always been the better experience.
Advantageous mp3 is a great little iTunes addition that sits unobtrusively in the application’s script menu. Search for a song or album on the iTunes Store, but before you click ‘Buy’ select Advantageous mp3 from the iTunes script menu and it’ll search Amazon MP3 for the song you’ve selected. You can then buy the cheaper, and higher quality, version from Amazon (if it’s available).
[via Lifehacker]
A big if in my experience. I frequently find that songs are available only by album on Amazon MP3 even though they are available as individual tracks on iTunes (and, less frequently, vice versa) or more expensive/the same price. That's assuming I can find the thing, Amazon does not have the indie connections iTunes has.