very nice, the curves are very well smoothed.
I think it could be better for the grasshopper component to scale the curves like Grasshopper is doing 1 pixel = 1 unit. So it will be more simple to put the image under the curves outputted by Vectorize. At the moment there is 72 pt/inch there so a coefficient 2.835.
Both the command and the Grasshopper component determine the images horizontal and vertical pixel-per-inch and scale the output curves based on these values and the model’s unit system. This is basically what the _Picture _1to1 command option does. The hope is to create curves of a reasonable size.
As for smoothing, you might play with the Corners parameter, which controls the smoothness of the traced curve. If your image has many colors, you can also play with the Threshold parameter, which coerces colors to either black or white.