The broadheads that give the best blood trails are the ones that cut major, high pressure arteries and make holes on both sides in the lower half of the chest cavity. If you're shooting down on a close shot from a treestand and have to place the shot high in the chest to get both lungs, then you'd better get a passthru if you want a good blood trail. Otherwise, the wound will do most of it's bleeding internally. The chest cavity will fill with blood until it reaches the level of the wound.