I am not sure what you mean by "Best Design software", But I draw in autocad, export as a dxf file, run it through Sheetcam (now in beta)
www.sheetcam.com , to generate the gcode and then use TurboCNC
www.dakeng.com as my controler.
To me, this is a powerful setup and for ME, it is easy to use.
I use autocad as I have it for work.
Sheetcam is extremely easy to use (and I might add generates good code time in and time out)
Turbocad is dos based, easy to use does the job and not overly priced.
Of course YMMV, but I am satisfied with this setup.
Bubba