Ive tried both Mach3 and USBCNC, and if your thinking of building a decent pc to cope with spitting out all them pulses (especially when you need to increase the Kernal speed) the my money would be 100% on USBCNC as the bored does all the hard work and using the ethernet cable makes it a doddle to setup and use. and for what it costs for a decent pc and bob its pretty close call with USBCNC