They are actually different spells.
The first spell is called attack from within (elemental). It deals elemental damage (air, earth, fire, or water), which in AU is easier to defend against (protection from elements is a 3rd level Simple spell). It does a mximum of 10d6 damage.
The second spell is called attack from within (energy). It deals energy damage (acid, cold, electicity, fire, or sonic). Energy is more difficult to defend against in AU (protection from energy is a 4th level Complex spell). It maxes out at 15d6 damage. The heightened and diminished versions of the 4th level attack from within are also more potent than its 3rd level counterpart.
Hope that helps,
-Sho