There are a variety of ways to find and download Android apps. The primary one is the searchable, browsable Android Market, available both on Android devices and the Web. So you'll be able to use the market to download apps on your Android device, or else download them to a PC or Mac and then transfer them to your device. The Android Market is wide open and does not have the same restrictive policies as Apple's App Store. Google, for example, doesn't ban apps based on their content the way that Apple does.
Google's Market isn't the only place to download apps. Others can set up download markets as well; Amazon is said to be working on one, as is Verizon. And GetJar recently raised over $40 million in venture capital funds to build a third-party app market for Android and other platforms.
In addition, you can download and install apps straight from the Web without having to go through any market -- but setup can be confusing when you download apps that way.
Android also doesn't have restrictive policies about development tools used to create apps for it. And Android allows the use of Adobe Flash on its devices, something banned by Apple.
This app openness can have drawbacks -- it means that no single entity vets the quality of the apps available for download. Instead, people have to rely on reviews by fellow users and professional reviewers. And there are concerns that because there's no central vetting of apps, hackers may turn to writing Android malware: Recently, more than 50 infected apps were pulled from the Android Market.
Android is more open than iOS in other ways as well. Notably, Android is open source, which means that manufacturers and wireless providers can customize it in any way they want -- even by cluttering phones with what you might consider crapware. For example, Verizon equips the Droid X with an app called VZ Navigator, a GPS tool designed to give you turn-by-turn directions. To use VZ Navigator, you have pay $10 a month for a subscription; if you don't want to subscribe and you'd like the app gone, you're out of luck -- it can't be uninstalled.
Another problem is that manufacturers and service providers don't have to include all of the features built into Android. For example, Android 2.2 and newer versions include built-in tethering via a USB connection, as well as wireless hot spot capability. But the Droid X, for example, only supports hot spot connections and doesn't include the USB tethering feature, even though it is perfectly capable of handling it.
Unless you want to jailbreak your iPhone, there's just one place to download and install apps for iOS -- the Apple App Store. It's simple to browse and search for downloads, and it's easy to install them once you've found them.
Unlike Google's approach to Android apps, Apple has chosen to be a gatekeeper for iOS apps: Developers have to follow a variety of rules about content, development tools and family-friendliness if they want apps to be available. Apple argues that this policy ensures that users get higher-quality apps than they would get with Android. The company also contends that it keeps potentially objectionable content out of the App Store.
Apple's policy is a two-edged sword. On one hand, it may in fact ensure that users get higher quality apps that aren't likely to cause problems on their devices. On the other hand, Apple doesn't apply its rules in a consistent manner.
For example, the company has banned some apps that featured women wearing bikinis but it has allowed others that come from well-known brands, such as Sports Illustrated. And it initially banned an app featuring the cartoons of Pulitzer Prize-winning cartoonist Mark Fiore because the app "contains content that ridicules public figures." After enduring a firestorm of bad publicity for that decision, Apple chose to allow the app back in to the App Store. More recently, Apple banned an app that allowed users to view the leaked U.S. State Department diplomatic cables made public by WikiLeaks; a similar app is freely available for Android phones.
That lack of openness extends beyond the content of apps. Apple also polices the development tools that are used to build apps for iPhones. In addition, it doesn't allow Flash on iOS, so users of its devices can't view Flash-based content. And Apple has raised the hackles of many publishers with rules about subscriptions to magazines, music and other media that allow Apple to take a hefty 30% cut of subscription fees, along with other requirements that content providers consider onerous.
Whether most iOS users know or care about these limitations is up for debate; with hundreds of thousands of apps available in the App Store, they may not feel they're missing out on much. In the end, the question is whether you want the most open platform possible or whether you're willing to let Apple be your gatekeeper.
Windows Phone 7
Windows Phone 7 falls far, far short of both Android and iOS when it comes to apps -- depending on whom you talk to, the number as of this writing was anywhere from 9,000 to 9,500. As a result, Windows Phone 7 users don't have anything close to the wide variety of options available to iOS and Android users.
There are a number of reasons why Windows Phone 7 has fewer apps. One, of course, is that it's newer than iOS and Android. But Microsoft also designed the operating system not to be app-centric. Android phones and the iPhone beckon with a plethora of engaging apps that invite you to run them; Windows Phone 7 has been designed to deliver information efficiently so you can complete the job at hand and move on to something else.
When it comes to openness, Microsoft's policy on Windows Phone 7 is closer to Apple's stance on iOS than it is to Google's approach to Android. You can download and install apps only from Microsoft's own store. It's not yet clear whether Microsoft will wield as heavy a hand in banning apps as Apple does, but there have been assertions that the software giant is already banning some apps from Windows Phone 7 Marketplace.
On the other hand, Microsoft doesn't restrict the tools that developers can use to build Windows Phone 7 apps. And the company hasn't specifically banned Flash from Windows Phone 7, even though Flash support is not yet available. Support is expected to come some time in the middle of the year.
If you want to have access to a wide variety of apps, you'll want iOS or Android. There are so many apps for each of those platforms that you'll be able to find many to do what you want, and I've found no discernible difference in the quality of apps written for iOS and Android. And if openness is what you're after, Android beats both iOS and Windows Phone 7.