Steppers or DC motor for Z axis THC

Hello - getting ready to work on configure Linuscnc with Plasma - I have a working 3 axis plasma table based on PnvConf.
driving Mesa 7i76. No THC at present.
BUT - my z axis from a legacy machine has a floating head driven by a dc motor not a stepper. Is it
worthwhile to convert this mechanically to a stepper and get better control when using Mesa 7i76 +THC-10?
From what I've read Plasma C can handle the DC motor when configured as External. But I'm worried about
relays and delay times etc. causing issues. All comments well appreciated.

tnx for your quick response - stepper it is
For those that are interested - this machine is only 1 month old - its
real nice mechanically (ArcBro Scout II from China) but the Fangling controller is 'delicate' and an intermittent short on one of the cabling pins took it out. Manufacturer refused to replace bad PCB. So here I am - so far thrilled with Linuxcnc and my own/manageable control hardware.