And neither of these trailers is as well built as an all aluminum trailer from earlier years. A used SILVER STREAK, AVION, STREAMLINE or even downmarket AIRSTREAM would be better. Cheaper to buy and longer lasting as well. The joke about todays square white boxes is that they are
ten year trailers on a twenty year note. They don't last.
An older, truly aero trailer -- especially one with independent suspension -- is the best bet for fuel mileage and overall costs. What may need to be replaced is straightforward (appliances are generic, as is flooring, etc), and there are large -- very large -- groups of enthusiasts. No need to break trail as it's already been done.
The separation between TV and TT is too great for wings, etc. Treat each vehicle separately.
Get a PRO PRIDE hitch. There is no substitute for a sway-eliminating hitch. The best the rest can do is resist sway. Same for disc brakes on the trailer. Mile for mile, towing
doubles the risk of a serious or fatal accident.
And, with that contemplated TV go read everything you can find from Andrew (Andy) Thomson of CAN AM RV in London Ontario.
RV Lifestyle - Hitch Hints & Wagon Masters
Pay special attention to tire/wheel combinations for the TV. Get good tires well matched. NOTHING will make a bigger difference except certified scale hitch rigging (assuming a PP hitch and disc brakes).
Fuel economy doesn't mean much for a traveler only moving 5k annually. It's the guys traveling 10k or more annually who benefit. Keep your speed to 58-62 mph at most. The trailers shown are about good enough to run up to the lake. In clear daylight, with no winds or semi's on the roads.
Depreciation and outrageous increasing maintenance costs make the trailer type shown a true money pit. Mpg decrease is only the icing on the cake.
Economy is the lowest cost over the most years. My folks had their aluminum trailer 27 years, and full-timed for nearly ten of those. They replaced the AC in that time. Nothing else.
I'm in the market for another aero aluminum trailer, and I keep my search confined to 1972-1990.
As to the other subjects on here, keep in mind that the tradeoff between aero and live-ability was worked out more than 50 years ago. The available power in cars, and the state of pre-Interstate highways made aero a highly viable subject. But most of the time spent with a trailer is not in driving. Today's excellent drivetrains, and the Interstate, make 15 mpg easy on a well-spec'd rig. I've seen 18 for European TD SUV's and new 25-28' Airstreams (heavy trailers).
The OP's van can tow a bigger, better trailer than the ones depicted for a lower initial cost, and, once repaired/upgraded, for a lower road cost. With FAR better handling and wind resistance (crosswinds). And an indefinite life.
Good luck
.