Without trashing telemarking too much, there are four indisputable advantages AT equipment enjoys over tele gear.
Locked heels transmit more energy and steering force from leg to ski.
If you're clinging to an icy 50-degree slope with 30 pounds of gear strapped to your back, worrying about pitching over the tips shouldn't be the first thing on your mind. That's good news in a crash because less torque on the knees means less chance of injury. Even more important, if you're caught in an avalanche, releasing from your skis can mean the difference between floating and sinking. AT boots have the grippy rubber soles and the crampon compatibility of mountaineering boots. AT bindings accept ski crampons, which let you keep your skis on your feet when your skins are sliding on ice or you're traversing a steep slope.