Answer:
The nonsymmetric solver is able to improve the convergence. However, it should only be activated if there really are convergence problems.
For certain material models, you may also be requested to activate the nonsymmetric solver.
In the case of the "normal" equation solver, it is necessary to save only one side of the matrix, as it is symmetric to the main diagonal. With the nonsymmetric solver, you have to save both sides and, of course, create them beforehand. This requires more memory and longer processing time.
For a model that converges well anyway, the nonsymmetric solver only leads to a longer computing time and is of no use.
