I've completed the Thieves' Guild quest line, and been awarded my choice of abilities. One of these abilities is the "Shadowcloak of Nocturnal" which causes me to become invisible if I crouch, but only for a few minutes once a day.
At the top of the Sneak perk tree is something similar called Shadow Warrior, except it is not limited to a few minutes each day.
How do these two abilities compare? Is it worth it to have both?