Subscriptions and purchases are beneficial in different ways.
You generally buy the music you love. As I said, I have mostly bought singles from iTunes and those that I liked the most ended up being CD purchases.
You buy what you "love" and you keep it to have "forever".
Does buying music online make sense? Not really. As I said before, I've purchased tons of music at iTunes. Several hundred songs. Now that I think about it, that was a complete waste of money. All but a few songs are DRM'ed. The sound quality isn't anywhere near as good as what you get with a CD or other online services. My ability to play them is also dependent on Apple keeping the iTunes authorization servers up. Let's look ahead 20 years from now. Let's say that Apple just happens to go under and I can no longer authorize my computer. Guess what? All those hundreds of songs are gone. Yet all of my CDs will still work. Unless I burned all of those songs to CD. But then I'd have to fish out those CD-Rs, hope they still work, and rip them again and suffer with further decreased sound quality due to a generation loss by using lossy compression on the song twice.
Then theres the fact that you're at the mercy of Apple or whoever thanks to DRM. Let's say Apple wants you to pay for some ability to continue to play your songs on new iPods or iTunes. Much the same way they're trying to ripoff/force people to repurchase their iPod games for their new iPods.
We already know that Apple is charging people to upgrade the sound quality of their songs (when all of the WMA services did it for free), how do we know they won't extend that kind of attitude to other areas?
The way Apple has dropped compatibility in the past, and now with the iPod games, how do we know that they won't require some kind of payment in the future to be able to continue to use our purchased iTunes content?
Buying is generally better than long term rentals. But when you're at the mercy of DRM, buying doesn't make sense. Because theres no knowing if your purchase will be rendered unusable and payment required to continue using it. Apple has done it before and theres no way of knowing if they'll do it again.
This is where music subscription services make sense. Yes you are renting, but you know what you're getting immediately. You're not getting into it think that the company is good, only to be ripped off later (iPod games, other issues). You know from the start that you are renting your music and it will disappear if you stop paying. You get as much music as you can handle for a small fee, you can sync it to a compatible player, and take it everywhere. If they upgrade the sound quality, you get that for free. If you want to "buy it" you get a discount, being a paid subscriber and all.
Considering how Apple has been treating customers lately........... with the issue with ringtones on the iPhone, locking out all but certified video accessories on the new iPods and refusing to release firmware that allows you to use what you want, making customers buy their iPod games again, build quality issues (like the tilted screen on the nano, bad screen on the iPod touch, all around build quality issues with the MacBooks and MBPs), renting music from Microsoft makes more sense than buying music from Apple and not knowing if they're going to find a way to charge you again for it in the future in some way or another.
I'm not the only one who feels this way either:
http://www.ilounge.com/index.php/articles/comments/11475/
I'm definitely close to finding buyers for all of my Apple products (iPhone included). I'd rather have a Zune and my HP notebook and know what I'm getting into rather than my MacBook and iPods and not know what Apple will do in the future to try to get more money out of me.