What's best, a usb controller or a parallel board for mach3 on a home built cnc router?

I would highly recommend the Mach3 USB controller: https://www.buildyourcnc.com/item/electronicsAndMotors-electronic-component-breakout-Mach3-USB-Board This board is very easy to connect and there are many detailed videos on how to connect and configure this controller. I would shy away from parallel port breakout boards unless you are going to use a controller that requires this breakout board as an add-on.