@raykholo reported on FB that the raster speed issue on smoothie is fixed?
If so the sucking sound that has been dragging me toward grbl has died down 
That would be great if they finally worked it out.
Have a link to what you are talking about ?
LightBurn’s developer has rewritten the smoothie firmware for faster rastering speeds. It is currently undergoing internal testing, but is almost ready to be released for the C3D boards running smoothie. I think it will only work with LightBurn, as the gcode must be generated specifficaly for the new firmware. I would readch out to @raykholo for more details.
Would this firmware also work for original smoothieboards? I would imagine so as the internal pinouts of smoothieboard and C3D correlate with each other.
Here is the announcement on the C3D forum.