The mesh command does not allow you to visualise the surface smoothness because of the triangular vertex lines that are always there. And up to Rhino V6 there is no way to take them out when you are making the mesh conversion. Is not possible to look to the quality of the mesh in realtime while you are changing the values.
SOLUTION: The best way I can think of is to make a Grasshopper tool with sliders for this:
You can add other add-ons to Grasshopper to control and disable, from the remote control panel the Display>Preview Mesh Edges
But using Grasshopper i was not able to preserve the UV mapping in the converted final mesh.
So I compy the Grasshopper parameters and apply mesh rhino function at the end of the process.