AT&T's packing the hot smartphones, and Aaron brings two of them together for a dogfight.  The Motorola Atrix HD is a newcomer to the carrier and is available for $99.99.  It packs a 1.5 GHz dual-core Snapdragon S4 CPU, 4.5-inch HD display with ColorBoost, 8-megapixel camera with 1080p recording, 1,780 mAh battery, and Android 4.0 with Motorola's UI, complete with a KEVLAR-coated back.  The Nokia Lumia 900 is available in multiple colors for $49.99 and offers a 1.4 GHz single-core CPU, 4.3-inch AMOLED display with ClearBlack technology, 8-megapixel camera with 720p recording, 1,830 mAh battery, and Windows Phone 7.5.

Both are 4G LTE devices, but beyond that, they're very different.  Which one is best?  Part 1 of 2.