best thing to do is try both and decide , I've used emc and have stated my concerns with it many times , mach worked out to be the better choice on my router .
After tearing down the router to make room for my mills , I still use mach . Ubuntu was much too resource demanding for my p4 pc's , mach runs multiple tooling (manual change)on my xp pc's flawlessly at roughly 50hrs/week and my pc's are rarely ever shut down or rebooted . Only problems that I've really had were hardware related .
I've looked at , and installed the latest version of linuxcnc into vmplayer , and I must say that there appears to be a large leap in linuxcnc . The new install runs great on vmware , its fast and clean (usually not so sh$@ hot on vmware). Which leads me to believe that it may have come around to a point that it's not so resource demanding and running much more lean . I really liked emc when I was using it but it eventually wasn't the right fit . The latest version looks pretty darned good and I'd probably cross over and try it before considering upgrading to mach 4 . I'll probably try an install when I can find the time but will probably stick to mach3 unless I see a noticeable difference in processing my heavy coded surfacing programs
Unfortunately this is always the touchiest subject that I have ever seen repeated on the forum because some people feel strongly in their opinions(both sides of the fence) and the one thing that is over looked is the time and effort that are put into both control wares . They are both fabulous for quick set up and play , with obvious tweaks to come , and both perform well . Some like a chevy some like a ford