Maces -> Heavily armored enemies.
Swords -> Unarmored enemies
Axes -> Evasive enemies or enemies with healing effects.
Daggers -> First Strike Ambush.
This is assuming you max all the perks in each weapon. Personally, I see axes as being the best "All Round" weapons, the Deep wound effect can inflict damage on heavily armored targets, and anything lighter in defense will probably just get hacked to death in a few moments.
Frankly though, that's all theory, the fact is, nobody will know until we parse DPS on each weapon type.