arc technica probably put it best (even if I do hate Apple)
As of November 2008, the Zune Pass allows its users to keep any 10 songs per month. In other words, if you wanted 30,000 songs for keeps, just like the iTunes Store, you would have to wait 250 years. The cost would be a whopping $45,000, however [compared to $30,000 to fill up a 120GB iPod]. In other words, it's only really worth it if you're OK with the fact that you have to keep paying the monthly fee to keep access to the songs that you don't yet own. Otherwise, iTunes (or any other à la carte model) is the way to go.
As of November 2008, the Zune Pass allows its users to keep any 10 songs per month. In other words, if you wanted 30,000 songs for keeps, just like the iTunes Store, you would have to wait 250 years. The cost would be a whopping $45,000, however [compared to $30,000 to fill up a 120GB iPod]. In other words, it's only really worth it if you're OK with the fact that you have to keep paying the monthly fee to keep access to the songs that you don't yet own. Otherwise, iTunes (or any other à la carte model) is the way to go.