I think it's important to look at units in all price and quality range. For example, a "light" unit might fit the bill, but compare it to a solid and well known "heavy" unit to understand the differences.
Compare weights, look underneath at tanks and valves, check tire sizes, and above all look in places where most people don't look. Often the build quality of a rig can really be determined by seeing what most people will miss. Solid wood versus particle board, hinges, trim boards, how things fit.
A 26 footer that weighs more might mean a stronger unit, a better frame, thicker wood. Buying a used unit from a few years back may be a better choice, but you have to know what to look for.