Building a death army for AoS and need help deciding what to build with my 15 horses. I like the base stats/abilities on the hexwraiths better but the Knights with a necromancer are pretty nice getting the same to wound roll as the wraiths and an extra damage on the turn they charged and the necromancer letting them pile in twice. The knights can also return models to the unit. Is this combo consistent enough to take the lesser unit? Or should I stick with the hexwraiths?