There's nothing that comes even close to the design and functionality of an Airstream. They tow exceptionally well, the interior space is used to its maximum effect and the exterior is, well, timeless; an American icon in fact. We wanted to buy only one travel trailer to see us into retirement and our Airstream, properly maintained, will do that. Yes, Airstreams are expensive, but over the length of time you can expect to own it, it represents pretty good value.
Whilst those properties are general, we were really sold on the specific interior fit, the Serenity, which moved away from the traditional wood paneling effect to a more contemporary feel. I know lots of Airstream folk love their "Classics" but for us this was one of the main selling points.