I have been using Mach3 since 2017 on my old computer with Windows XP. It is time to upgrade due to computer failure. I have a Taig bench top mill with a Gecko G540 controller. I plan on using windows 10  on a new (I know 10 is obsolete now, but I have the computer already) would it be better to used the UC100 motion controller or to install A parallel port in the new computer?

There are 'for' and 'against' for each but my personal choice would be to use the UC100.

Tweakie.

Mach3's parallel port driver will NOT run under Windows 10 or any OS newer than Windows 7 - 32 bit version.