Aluminum Can or Plastic Box? If you are willing to spend that much for a new Airstream you might also look at an Oliver, a double-shell molded TT in the same size range. That would make it three totally different types of construction.
I would add Bigfoot and Escape to the list, except that a Bigfoot on that size range is probably too heavy for you, and I'm not sure what Escape is currently building, there have been stories about moving production from Canada to the southern U.S.
I can't say much about the Lance, because they are not showing in this area, so I haven't looked at what goes into materials of their conventionally constructed (laminated walls fastened at edges) TTs to make them twice as expensive as the cheap TTs everyone else builds.
Molded plastic hulls as TT shells (Oliver, Escape, Bigfoot and some other brands in smaller sizes) I understand; that's how small ocean-going yachts are built. It is the egg-shell principle.
Metal semi-monocoque shells (Airstream, Avion, Spartan) are an application of 1930's aircraft fabrication technology adapted to RVs initially to make use of factories and skilled workers no longer needed to make warplanes. It bothers me that Airstream assembles a partial hull atop a floor. I know they are sturdy, I don't know how they weather. I do know that really old ones are quite valuable, like antique luxury cars.
Most of today's lightweights are assembled atop a floor, using laminated panels on the sides, maybe on the ends, fastened to roof and floor structures at the edges. There is a lot of variability in materials used, methods for contructing floors, roofs and ends, and since most have slideouts, how those are built and supported. Forest River, Keystone, Dutchmen, K-Z, all make lightweights this way. Most mass production motorhomes are made the same way. Lance and Evergreen use the same construction principle, say the difference in material makes them worth a lot more.
Tom Test
Itasca Spirit 29B