The Android Market has far more apps than BlackBerry's App World but less than Apple's App Store. However, with Android apps numbering 300,000 compared to Apple's 350,000, that gap is closing fast. There are more free apps on Android than in the App Store. Popular games such as the Angry Birds series, which iPhone users must pay to use, are free from the Android Market.
Android smartphones can also run apps from any source, whether the official Android Market or a thread in a developer forum. Before you make your purchasing decision, consider the pros and cons of a curated experience, where a company like Apple extensively tests apps before you download them. iPhone apps just work -- if they didn't they'd never make it to the App Store. Android smartphone users often play the role of beta testers, sending reports to developers as apps crash, force-close or drain too much battery. On the plus side, there is nobody to censor or decide what apps are appropriate for you to run. If you're a fan of the Bittorrent protocol, video game emulators or not-safe-for-work content, Android will have you covered, Apple not so much.
There's also an entire category of apps, called widgets, that you won't find on other smartphones. These useful apps sit on your homescreen to provide glancable information about the news, the weather, or the latest updates from your social networking accounts. As you can see, Android has pros and cons when it comes to the app experience.