Actually, it is not about Maps at all. Maps is merely an application built on Geolocation. It is actually all about the data associated with geolocation.
And that is where Google scores. Because they have the best and most extensive and fastest growing databases linked to geolocation.
The Google ecosystem of apps that use geolocation include the Google Apps (Maps, Local, Places, Drive, Calendar, Tasks, Picasa and more) and third party apps (like the location based todo app that I use).
The problem today is that all these apps do not yet form a true ecosystem. They do not use the Google APIs yet. Google's own iOS apps like Google Local, open up the clunky Google Maps on Safari, instead of the easy to use and smooth Google Maps native iOS App.
However, that will change quickly. All of them will quickly start using the Google APIs. How else will they survive? The best location apps will use the APIs with the best data. And that is Google today.
As for iOS vs. Android, it is the same old Mac vs. Windows story. We all know how that turned out. The best hardware will not win. Nor will the best OS. The ecosystem of applications that consumers start using, will determine which one wins. Google apps clearly show the way today. Tomorrow... Who knows?