The letters are more "ugly", because Mach3 has problems with it's trajectory planner.
The lower your acceleration will be the worse this will get and the larger the difference of acceleration is between your XY axis (because those axis plays in this code interpolation) again the worse it will get.
Also you don't know how much error the machine will make on the path in CV mode, there is no parameter to define it in Mach.
With the UCCNC there is no such problem, the trajectory planner has no defects like this, the CV controller has path deviation parameters,
so you can exactly define how much the software can go off the path in order to make the job as quick as the CV parameters allow.
The larger you set that the faster the software will finish, but the worse the tolerance will be and the lower you set the CV deviation the slower it will finish,
but the better the tolerance will be. You can define the deviation in the working units (mm, inches, etc.), so you can exactly set the wanted tolerance for different jobs depending on if a job needs accuracy or speed or in the midway.