Which scheme is better for Goldsmith (Jewellery job worker, not seller) - Regular or Composition ?

GST rate for SAC 998892 (Jewellery job workers, not sellers) is 18% (if undertaken on goods belonging to unregistered persons) and 5% (if undertaken on goods belonging to registered persons). Is there any ITC available? if yes, then on which items ITC can be claimed ?

Also the GST rate in Composition Scheme is 6% for SAC 998892. No ITC available.

So, please tell me which scheme is tax saving ?