Android is a software stack for mobile devices that includes an operating system, middleware and key applications. The Android SDK provides the tools and APIs necessary to begin developing applications on the Android platform using the Java programming language.

Android can Run Multiple Apps at the Same Time: The current version of iPhone OS does offer limited multitasking, but only allows native applications such as Mail, iPod and Phone to run in the background. Android users benefit greatly from this discrepancy, as they can receive notifications, listen to music, or even record GPS data without keeping the application open. Android Keeps Information Visible on Your Home Screen: Android has is a customizable home screen which keeps active widgets right at your fingertips, always accessible and always visible without having to launch an application first. Android Has a Better App Market: It's true that Apple's App Store has over 180,000 applications, while the Android Marketplace has only just broken the 50,000 mark but Android rapid growth and adoption give it the potential to catch up to the iPhone App Store. Android also has another advantage: a completely open market. Android Gives You Better Notifications:

The iPhone has some trouble with notifications. Because it's restricted to pop-up notifications, it can only handle one at a time. Android Lets You Choose Your Hardware: Apple users are encouraged to Think Different but when it comes to the actual hardware, they don't get much choice. Android Lets You Choose Your Carrier: AT&T truly is the iPhone weakest link. The iPhone success turned the country fastest 3G network into a staggering mess of dropped calls and dodgy data connections. Android Lets You Install Custom ROMs: Android has a small community dedicated to building custom ROMs for Android devices. Not only do Custom ROMs bring the same functionality Jailbreaking does, but they also bring an additional level of customization to your phone. Android Lets You Change Your Settings Faster: iPhone users are stuck digging around in the system settings every time they want to use the internet or a Bluetooth device. Android lets you use widgets to manage your settings directly from your home screen Android Does Google and Social Integration:
The iPhone can do this only through use of third party apps, and is nowhere near as seamless to use as the Android alternative.
Android Gives You More Options to Fit Your Budget: Every major cellular carrier (except for AT&T) has at least one Android phone available free with two-year agreement. Of course these are lower end Android devices, but they are still comparable in performance to the iPhone 3GS.