Both in item summon , with souls...
But for the sword, if you don't need to complete equipement, dark= inferno = lightining... they are tier 16 sword, with 8 stats. The name of the sword only change it's appearance (not the same if you get a full set)
Different for wings: inferno wings are better than holy wings bcz they got more stats, are tier 16 (holy wings are tier 15, as blizzard and berzerkers) , and can be a bonus to inferno set if you have it full. But i only got holy wings in the shop.