However, the big disadvantage modern laptops have for use with Mach3, is that they rarely come with a parallel (or printer) port.
An advantage the desktop has, is that a used one that's quite capable of running Mach3 can be bought for very little money and can be a permanent part of the CNC installation.
M
I would challenge you to find any new PC - laptop or desktop - that comes with a parallel port. The days of the parallel port are over for any computer, as that technology has been surpassed and replaced by the USB port. Also, for thiose who insist, there are still many used laptops for sale that have parallel ports, although I would not waste my time, energy or money on one myself.
I, instead, purchased a converter that gets me over all of that, called the 'UC100', and is available from CNC4PC for $129.00. No more do I have to worry about tracking down a PC with a parallel port. I also don't have to worry about replacing any of my breakout boards, as the UC100 has a DB25 connector on one end and a USB connector on the other. It works very well and is designed especially for Mach3. This was $129.99 well spent.
Jim