When I built my machine a few years ago I went with UCCNC. Never tried Mach3. Never regretted the decision and never looked back. Great software/hardware, great support.
Made this for the wife a couple of weeks ago. But when it got to the end it had lost quite a few step unfortunately but managed to save it. Hopefully the lost step issue will be fixed shortly. http://www.forum.cncdrive.com/viewtopic.php?f=2&t=2297