Witch of the Veil or Shadowcaster for Lich run?

I want to create a sort of shadow lich for the new run, and I am torn between two choices: Witch of the Veil or the Shadowcaster? Both will be immensely powerful with merged spellbook, but RP-wise I am not sure which one to choose. Witch of the Veil Lich would be able to slip into the shadows and appear anywhere on the battlefield. Shadowcaster would be able to turn into the shadow and summon a powerful shadow as well.

What is your opinion?