2Airs point about differences is central. Still, among the aero alu trailers there were some basics, so lets' take it through about 1985:
Airstream had the roundest cross-section, lowest ground clearance and torsion axles.
Avion (after 1967) had, first, a walking beam suspension, then changed to a fully independent suspension about 1977.
Silver Streak always had live axles.
Streamline (defunct in 1974) also had live axles.
Live axle is fine to a point, then it isn't. So, let's hypothesize a pair of 1989 trailers, AV and AS and spec them as close as possible, both for best balance front/rear and side/side. Full fresh water and propane. Upgrade them with disc brakes and sway eliminating hitch. Top speed of 75 mph. No matter the road or winds we're not, I think, going to see enough of a difference. The TV is the weak link.
As to fuel mileage with this pair it will be the driver. That is, with the same TV on either trailer the fuel mileage variance -- outside of a wind tunnel -- is driver dependent. Even with the nastiest 3/4 angle crosswind.
If we wanted to play with all these trailers to derive the best ideas, then the all-aluminum STREAMLINE cabinetry (riveted to walls and floors) would be a great addition. As would it's and AVION three main channel frames. And Silver Streaks seam sealing. Or its and AVION fit and finish. AVION or STREAMLINE spray in insulation and anyone but A/S complete double hull. But A/S cross section. Etc.
Aero and independent are what matter most for alu trailer "performance". Disc brakes and sway eliminating hitch bring all of them up to speed. I couldn't shake my live axle S/S with violent lane changes, throttle-on at over 50 mph back and forth across an empty Interstate once I had a Hensley. Maybe not an A/S, but a real improvement. Mpg in sig.
1990 35' Silver Streak Sterling
; 9k GVWR.
2004 DODGE Cummins 305/555; 6-manual; 9k GVWR.
Hensley Arrow. 10-cpm solo, 18-cpm towing
Sold: Silver Streak Model 3411