I have seen many enthusiasts in the design, fabrication and installation of triangular cross section composite truss. From experience, are there any clear advantages of using such trusses?
Generally, the design is lightweight compared to the load it will support. It is also a rigid structure.
An argument could be made to say it is an efficient use of materials and space.
Some trade-offs are:
A longer construction time needed to weld, bolt, or otherwise secure each component.
The piece must be custom made for the application. You can't simply add or remove material to improve the fit.