I'm very comfortable on Linux and was thinking of going with linuxcnc over mach. I can develop and/or write my own stuff
If you are going to slave your x axis you might have to re think Linuxcnc unless you drive both screws from one motor. Linuxcnc don't seem to have a system for homing 2 motors (joints) there is a lot of debate over on the Linux forum about this. Its a shame its not been sorted by now. I use linuxcnc for my mill and Mach3 for the router. Driving both screws from one motor is no problem though. Good luck with the build. ..Clive