[JeffS]

I can't speak for the Tundra but for my F250 - Fords Towing guide for Maximum Loaded Trailer Towing shows a difference of 1,900 lbs Conventional vs 5th Wheel Towing:

2013 6.7L F250 SRW 4X4 3.55 axle
Conventional Towing max = 14,000
5th Wheel Towing max = 15,900

I realize this is just one dimension but in respect to tow load they do show a difference.