There are a number of materials used to create expandable frames from pop up booths. Fiberglass, aluminum and plastic to mention a few. Experience has shown that aluminum has been the most popular. Rigid frames need fewer connecting points that flexible plastic or fiberglass, but don't be fooled. There are many types of aluminum.
Some aluminum is manufactured to be more rigid given the same thickness.
Some aluminum tubular frames have a thicker wall than others. Obviously, a more rigid type of aluminum, as well as a thicker tube wall would make for a more durable display. Like frames there are many channel bar types. Aluminum U channel with magnet attached to the front is the most often used. The thinking here is that aluminum is lightweight, which it is.