Usage of 'Anti-Backlash Nut Block for 8mm Metric Acme Lead Screw'

Hi,

We are planning to use 8mm ACME Lead screw for the Z-axis in our new 3d printer. When we saw the Open-builds videos with ACME lead screw, mostly they are using only 'Nut block for 8mm ACME'.

Then what is the use of 'Anti-backlash' nut.

For Z-axis with ACME lead screw, which one is the best - Nut block or Anti-Backlash nut block?

Thanks in advance.