The lattice tube design has two major advantages: with large telescopes in the observatory class, this design saves weight. Also, for a mirror size of more than 16 inches, the truss-tube construction is the only option.
Besides their weight, the most important advantage of Dobsonian telescopes is the fact that they can be dismantled into smaller parts. Only then are large Dobsonians small enough to transport them in the dark. The centre of gravity shifts toward the main mirror due to the truss-tube construction. With a Dobsonian telescope, the rocker-box build can be shorter - another advantage for transport.