I'm sure you meant 0.2 and 0.1 ohm. :)
But anyway the 0.1ohm variant allows to set a higher current value than the others. That doesn't mean the driver can stand this current, so be careful not to overheat the driver.
It would be most suitable for the extruder, because it's often the stepper which needs more torque.
The Z-axis could also benefit from more current when you have two steppers running in parallel config. ( not recommended, but still common practice )
-Olaf
But anyway the 0.1ohm variant allows to set a higher current value than the others. That doesn't mean the driver can stand this current, so be careful not to overheat the driver.
It would be most suitable for the extruder, because it's often the stepper which needs more torque.
The Z-axis could also benefit from more current when you have two steppers running in parallel config. ( not recommended, but still common practice )
-Olaf