Hello Jim,
For a rack and pinion, linear toothed belt or a high helix lead or ballscrew, holding torque is definitely important. A heavy uncountered mill Z axis as well.
But for acme leadscrews, allthread and the like, (hobby stuff), running torque is all that really matters. Once in position, there is (virtually) no torque required to hold it there. Just like manual lathes and mills.
Even with the ballscrews on my lathe, there is far less torque needed to hold than to feed a heavy cut.
Thanks,
RC