Napster v. iTunes: By the Numbers (Part 2)

To begin with, here are some more quick facts about Napster's rental model and the iTunes Music Store:

	iTunes Music Store's Purchase Model	Napster's Rental Model
File Type	Protected AAC	Protected WMA
Kbps	128	128
Number of Computers on which Files May Be Used	5	3
Number of Times a Track Is Burnable to a CD	Unlimited	Burning not permitted
Number of Times a Playlist Is Burnable to a CD	7	Burning not permitted

Napster seemed to be a little shy to tell users how many CDs they could burn and how many computers their protected files may be used on; I had to dig up the above states from Napster's Terms and Conditions. Apple had the number of computers right on their iTunes Music Store page, while I also had to dig up the number of CDs burnt per playlist in the terms, although I'm pretty sure that it was previously closer to the front.

WMA seems to result in smaller files at the same bit rate than AAC and thus quicker download times...
While a brief traipse around the net didn't get me the exact numbers, at a given Kbps rate WMA files are considerably smaller than AAC files, approximately half the size. As download times are a direct function of the size of the file and the speed of your connection to the server, smaller files will accordingly be faster to download.

... but AAC seems to result in higher quality at the same bit rate than WMA.
Based on information provided by Dolby, Apple says that "AAC compressed audio at 128 kbps (stereo) has been judged by expert listeners to be "indistinguishable" from the original uncompressed audio source." However, as "[t]he AAC codec in QuickTime 6 builds upon new, state-of-the art signal processing technology from Dolby Laboratories, both Apple and Dolby are clearly interested parties.

Nevertheless, this is confirmed by at least one assumedly disinterested third party.

The AAC file . . . held pretty much true to the original WAV file in terms of level at low, mid, and high frequencies. The only major deviation from the WAV file was in the 20 kHz+ range, which we cannot hear anyway. [The WMA file] had, however, a curiously low frequency cutoff at around 14 kHz, well within the range of human hearing. If the [AAC, MP3, and WMA have] to be ranked according to their quality/size ratio, the order would be AAC, WMA, MP3. . . . [F]or AAC and WMA, the biggest difference was clarity. At the same bit rate, AAC offered a clearer and closer sound to the original, beating out WMA.

Napster's protected WMA files can only be played on 3 computers.
Apple's got this beat with 5, but neither of them are particular satisfying, even though Apple's concerns are reasonable. We share in my family, my computer, my wife's computer, my mom's computer, and my sister's computer. So Apple's 5-computer limit works for us now and will for a one more expansion of our collection. Napster is a more stingy and wouldn't work with the way we currently use our purchased music, but I assume that those who only buy music for themselves will never even hit this consideration.

If Napster loses the rights to a song, you lose that song from your library.
Not only will you lose the song if you stop subscribing to Napster, but you'll lose it if Napster and the record label's agreement ends.

Loss of Rights by Napster. Napster may at any time lose the right to make certain Tracks and/or Materials available. In such event, you will no longer be able to obtain these Tracks and/or Materials or to utilize the "Sync/Restore" function for Purchased Tracks.

This is a problem under the rental model; if the intellectual property rights owners decide that they don't want you to be able to rent their intellectual property any more, just like that it's gone from your library. The purchase model, in either Napster or the iTunes Music Store, will let you keep that song, although it only makes sense that any sync/restore function for purchased tracks disappears.

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