Pickup Trucks.com put the 2013 Ford F450 and Ram 3500 HD through a series of towing tests. With 16,000 lb on gooseneck trailers, the trucks were tested at low and high altitudes. Both trucks performed well. The Ram had superior control on long descents, and was named the winner.
http://special-reports.pickuptrucks.com/2013/10/king-of-beasts-overview.html
http://special-reports.pickuptrucks.com/2013/10/king-of-beasts-overview.html