Unicorn hair normally makes the most consistent magic. All wands that contain the Unicorn cores are generally the most difficult to turn to the Dark Arts.
Dragon heartstrings produce wands with the most power. Dragon wands learn much faster that other cores. The dragon wand tends to be easiest to turn to the Dark Arts.
This is the rarest core type. Phoenix feathers are capable of the greatest scale of magic. Phoenix feather wands are always the pickiest when it comes to potential owners.