Out of my own experience I can recommend exocad. As I have to mill both files from exocad and 3shape, the latter has somehow more problems with milling. I have examined the output files and 3shape has artifacts near margin line on way too many occasions and those cant be smoothed out. That leads to problems with milling them.
We had this same problem. You have to re-snap the margin reinforcement (not using the right term here I'm the exocad guy) after modeling or your output stl will have ****ty margins.