Android gets apps from Google Play, which currently has 600,000 apps available, most of which will run on tablets. However, some Android devices, such as the Kindle Fire, use separate app stores that have a smaller selection of apps available. Many originally iOS-only apps are now available for Android, including Instagram and Pinterest, and Google’s more open app-store means other exclusive apps are also available, including Adobe Flash Player and BitTorrent. Android also offers access to Google-based apps, such as Youtube and Google Docs.
The Apple app store currently offers 700,000 apps, 250,000 of which are available for the iPad. Most developers prefer to develop games for iOS before they develop for Android. Since a recent update, the Youtube app has become unavailable on iOS, but iOS still offers some exclusive apps, including the popular game Infinity Blade and Twitter client Tweetbot.
The bottomline when comparing Google and Apple's app stores is that most popular apps are available for both platforms. But for tablets, there are more apps designed specifically for the iPad while Android tablet apps are often scaled up versions of Android smartphone apps. Developers at startups often focus on one platform (usually iOS) when they first launch their smartphone app because they do not have resources to serve multiple platforms from the get go. For example, the popular Instagram app started with iOS and their Android app came much later.