In fact, this discussion is pointless. A good quantity of apps is good, in a way that "ecosystem" have "critical mass" (more developers supporting it, more likely to have all the needed good apps covered).

But there's a point where the size difference doesnt matter - iPhone have 10 times more apps than Android available, but Android is nowhere near of lacking the good/interesting/whatever apps.

For a good measure, WP7 app pool can be more than enough to give the user a solid experience, appwise.

Since the N9 have most of the use cases integrated to the system, it can have a solid app selection with a fraction of that

What is very plausible, aren't the OS coming with even more software bundled? As the need for application grows, companies add more functionality out of the box to the OS. So today apps and programs for some measure are just "patches", to add to the OS a function that was supposed to be there from the start, by the user perspective - like DVD burners, backup systems, media players, etc - and for phones: twitter, facebook, email, skype and such.