Whether the priority is price or platform, those using AT&T have a plethora of smartphones to choose from.  Two of those devices are the Sony Xperia ion and Nokia Lumia 900.  Both are available now for $99.99, and offer 4G LTE connectivity.  The Xperia ion sports a 1.5 GHz dual-core Snapdragon S3 processor, 4.5-inch HD display, 12-megapixel camera with 1080p HD video recording, a front-facing camera, 1,900 mAh battery, and Android 2.3 with Sony's Timescape UI.  The Lumia 900 offers a 1.4 GHz single-core processor, 4.3-inch Super AMOLED display with ClearBlack technology, 8-megapixel camera with 720p HD video recording, a 1,830 mAh battery, and Windows Phone 7.5.

they're both well-equipped smartphones with strong feature sets, but only one can come out on top.  Which offers the best balance; is it the Android or the Windows Phone?  Part 1 of 2.