Be careful on the payload comparison between the manufacturers. Ford, for example, pushes their GVWR rating very close to their axle ratings. Until recently, GM had a 1000 lb difference between the two numbers, but their new truck ratings appear to be following Ford's path (smaller difference between GVWR and axle ratings). My '08 GMC 1500 has a GVWR rating of 7000 lbs, but the new '14 model will have a 7200 lb rating (which is still far more conservative than Ford). The spring and axle load ratings between the '07 and '14 GM models are identical, so that shows how the game goes.
My own opinion, from climbing under the Ford and Toyota and looking closely at components, is that the Tundra will handle every bit the load that the F150 "max tow" will, as will the GM twins. All require a solid WD system, and none will carry a load like the 250/2500+ series.