In my opinon you can not compare these devices,

The iPhone is made for the big market, its made for "Users" who dont want to think and want to play with their devices and to install much rubish on theris mobiles

The N900 / every Maemo device can be used by "users" if they dont play around with apps etc. but if you want to for the reason its made for you must be a techie who knows what he does an wants solve problems an play around and is not afraid to reflash etc.

both devices have their benefits and you have to decide waht you prefer...