actually HSS steel is like a low grade or medium grade in tool steel like drill bits carbon steel is the lowest then HSS but I belive HSS has a wide range of propertys or Qualitys to cutting tools. Carbide is much harder perhaps tougher I dont know all the terminology but When I worked in a machine shop carbide lasted much longer. of cource carbide dies Ive never heard of .
Ive used and abused 00 dies on a ridgid 300 in the field we would just use the machine with hand dies.
Im not familiar with 2 differant type die materials .
Id actually go with whichever is highest possible quality And Im not sure which it is or the price differance but if its like 20 bucks differance Id just want to get the better. because Ill only buy one more set of dies in my lifetime for hand threading LOL