"frontal mass of the camper and speed" are the main things I noticed. My last TT was a 29 foot Aspen Trail with a standard suspension. It was around 7K loaded 900 lbs tongue weight. I got the same mpg's with it as the new trailer a 30 foot Rockwood ultra lite I have noticed this year. I did put a road armor suspension on the Aspen Trail and it helped the driving characteristics, but the Rockwood has a torsion axle suspension and the smoothness and ride characteristics are much better out of the box.
So, I am pulling more weight, but definitely the mpg's are very close to the same... Not sure if the suspension is part of the equation or not. I have less sway and it tracks like it is connected now. Same tires as in Good Year Endurance.
One factoid I noticed was that I had aftermarket Endurances on my old trailer while the new one has OEM versions. I had a season and a half (8Kish miles) under my belt on the Discount Tire endurance's and they still had more tread on them than the new OEM's on the new Trailer. I thought that was interesting... I guess that's one way to cut costs is to reduce tread on OEM trailer tires vs after market. I'd say a good 10K year of life is about the difference for me as the driving consumer. AND, they put a China Bomb "Castle Rock" on as my spare tire... I guess the dealer could have done that, but didn't look like it.