One of the primary factors in choosing, though, may be the other devices and applications you use. If you use Mac OS X and/or have an Apple iPad, you may lean toward the iPhone 4 for the consistent experience, and the ability to share many apps among your devices. If you rely on Google Docs, Gmail, and other Google products, the Android device may make the most sense because of its seamless integration with the Google ecosystem.

But, if you use Windows, Microsoft Office, SkyDrive, and other Microsoft tools and products, the Lumia 900 may be the way to go. Microsoft has developed a . Windows Phone is unique, and innovative, and the Lumia 900 will most likely give it some badly needed momentum.

When you walk into AT&T with your $100 on April 8, though, think about the pros and cons of the different devices, and how your smartphone will mesh with the other tools you rely on, and choose the one that best meets your needs.