The main difference between the DW779 and DW780 is the laser guide system. The DW779 does not have a laser, while the DW780 comes with a built-in laser guide. Both models have a powerful motor, a 12-inch blade, and offer precise cuts, but the laser guide on the DW780 helps improve accuracy by projecting a visible line onto the material being cut. Another minor difference is in the weight of the saw. The DW779 weighs 56 pounds, while the DW780 weighs slightly more at 57 pounds. Aside from these features, both models are quite similar and offer excellent performance for woodworking projects. Whether you choose the DW779 or DW780 depends on your preference for having a laser guide system.