in table 8 wire awg 18-8 have two listings for ohm/1000 ft obviously solid and stranded which brings me off topic as to why there isn't two listings for #6 since nec requires #4 or larger to be stranded.
anyway is stranded wire less resistant than solid which would make it the first listng?
Good question. The table entry for #6 shows only the stranded info, but I know for sure I can buy #6 bare solid for grounding.
You can tell solid vs. stranded by looking at the "quantity" column: 1 = solid, 7 = stranded (7 strands). In all cases, stranded wire has a slightly higher resistance per unit length than solid, so I assume the same would be true of #6.