Travel trailer "vs" fith wheel --MPG to tow

I was towing our 27' square box TT in a rain storm and glanced back in the mirror. The rain was swirling 57 different directions in front of the trailer. Turbulence = wind resistance. That trailer weighed about 6400 lb. loaded. Switch to second trailer, a 27' fifth wheel that weighs 9400 lb. loaded and is about 1 1/2 ft. taller, but has a very rounded plastic front cap. Our mileage subjectively seems to be the same to maybe .5 mpg better. I think that rounded front everywhere (top, sides, bottom) makes a bunch of difference. Now even though the air is flowing smoothly around the nose there is still a lot of it at highway speed. I've had fairly heavy objects blow around in the bed of the pickup since getting the fifth wheel. As I look at big expensive very square nosed fifth wheels out of the highway, I wonder if that square nose cuts their mileage compared to mine. But then I realize that if they can afford that $100,000 fifth wheel, they can afford the fuel.