Well, you can see real users in the forum, in the what I've made with my machine ... area.
E.g.:
viewtopic.php?f=5&t=20467 millions lines of code ran for 3.5days long.
And it does not really matters for the UCCNC how long your code is, it will not load the CPU more if the code is longer, however ofcourse your videocard will be loaded more with the larger toolpath to display.
If your video card is weak then it does not matter how strong your CPU is, it will overload your CPU, because then the video card cannot do the job and then the CPU has to do it.
For computation other than displaying the UCCNC requires very small computing power.
UCCNC has path deviation control similar to how industrial controllers work, Mach3 does not.
With mach3 you can only guess about how much error it will make on the paths, you cannot set the workpiece tolerances.
Yes, mach3 is fast, but it is only fast, because:
1.) it has no path deviation control, so you cannot define the tolerances for the jobs. It will round corners and remove details from your work as it wants to.
With UCCNC you can define the tolerances exactly, for example you can tell the controller to optimise the path with a maximum path error of 0.05mm and then it will only optimise to that level.
2.) it's trajectory planner is broken, it overaccelerates/deccelerates your settings causing jerks. 2x overacceleration is very usual while we even measured out 8x overaccelerations with some extreme axis settings.
For this reason ofcourse mach3 is fast, but in the same time you have to realise that you have to downtune the acceleration parameter in real world compared to what you can set in UCCNC, otherwise your motors will loose steps.
In other words in the UCCNC you can set your axes accelerations at least 2 times than what you can setup in mach3 to make it work the same safe!
And this means that the UCCNC will be faster with the higher accelerations and it will still keep more workpiece details with lower tolerances than mach3.