Apple's (NASDAQ:AAPL) iPhone has several advantages over rival handsets running Google's (NASDAQ:GOOGL) Android, the biggest of which may be app availability. Although they typically make their way over to Android eventually, many of the most successful apps have started off as iOS exclusives. Electronic Arts' (NASDAQ:EA) popular new mobile game, Plants vs Zombies 2, only recently made the jump to Android after launching on iOS this summer.

But things are slowly changing. More developers are seeing Google's Android as their primary platform, and while Apple's iOS remains the more lucrative operating system to code for, the monetization gap is slowly closing. If Google's Android becomes the preferred platform for developers, it would be severely detrimental to Apple's business.

When it comes to succeeding as a mobile platform, apps matter
Consumers in the U.S. spend an average of two hours and 38 minutes per day on mobile devices -- 80% of that time is spent in apps, according to analytics firm Flurry. Simply put, apps matter. 

The only advantage a smartphone really has over a feature phone is its ability to run apps, and the quantity and quality of the apps available determines a given platform's success. BlackBerry's new BB10 handsets may have offered the best user interface, but that doesn't matter when you can't play Candy Crush. Microsoft's Windows Phone has been slightly more successful, but remains in distant third place -- the Windows store has more apps than BlackBerry World, but certainly fewer than Apple's iTunes and Google Play.

Apple has long benefited from robust developer support
Since its inception, Apple's iOS has been the preferred platform for mobile developers. Generally speaking, apps get developed on iOS, and then, if they're successful, they eventually get ported to Android. Numerous examples abound, including Instagram, Tinder, and the aforementioned Plants vs Zombies 2.

The sequel to Electronic Arts' wildly successful tower defense game finally hit Google Play in October, more than two months after launching on Apple's platform. Two months might not sound like a long time, but for gamers, it's a big deal. According to Giant Bomb, a gaming-focused publication, Apple went so far as to pay Electronic Arts a "truckload of money" to delay the game's Android release. Apple denied the report, but Giant Bomb stuck by its story.

Regardless, Electronic Arts' game has definitely become a premium app. Shortly after launching, it rocketed to the top of Apple's app chart, becoming the most downloaded game in August. Its popularity has dissipated somewhat, but as of this writing, the Electronic Arts'-published title remains among the 100 most commonly downloaded apps.

Developers are starting to think Android first
Worldwide, 34% of mobile developers now consider Google's Android to be their primary platform, more than the 33% that focus on Apple's iOS, according to Developer Economics, and Flurry reports that there are now more mobile app projects being started on Google's mobile operating system than on iOS. In terms of monetization, the average developer on Apple's iOS still brings in more revenue per month than the typical Android developer, but Vision Mobile reports that the gap is now down to around 10% (via Business Insider).

These figures may seem skewed in the sense that they're global -- in North America and Europe, developers continue to favor Apple's mobile operating system. But in Asia, Google's Android is dominant. For consumers in the U.S., that might not matter much -- many of the apps they use on a daily basis were likely developed in the West. Yet, for Apple itself, an Android-first developer mentality could stymie its global expansion.

Moreover, the possibility of an Asian app import boom looms as a potential threat. Flurry (via Computerworld) warned that Android apps made in Asia and exported to the West could eventually tip the app market in Google's favor.

Developers! Developers! Developers!
At this point, Apple's iOS platform appears to have enough momentum to sustain a dedicated developer community; becoming a minority platform and losing developer support (like BlackBerry's BB10 and Microsoft's Windows Phone) seem unlikely.

Still, Apple's app advantage remains one of its single largest selling points over Google's Android: To lose it would be a huge blow. Developers favoring Android should be one of the most worrisome trends for Apple's shareholders -- and they definitely should keep a close eye on the situation going forward.