Urad Dal is one of the most under rated pulses of South India. Other than idly/dosa batter or medu vada, not many use it in other preparations. Urad dal is available with its skin on or with the skin removed.
Its totally one's choice as to what you would want to use, but the colour of the dish would vary because of the colour of the husk. Black gram requires only minimal soaking -- about half an hour -- before cooking, which takes another...