I think you guys should use UE4 over Unity.
Secondly, Unity seems to be designed around a brightly colored, cell-shaded, look, while the Unreal Engine goes for flat our realism. So, for a game like this, I would recommend using UE4. Plus, if you use UE4 your developer street-cred would go up by leaps and bounds.
https://www.unrealengine.com/what-is-unreal-engine-4