What’s so special about Demonic Tutor?

So I’m confused, my friend told me to pick up a card called Demonic Tutor for my white black commander.

I looked at it online; it does the same thing as Diabolic Tutor and yet it costs $50 more.

I get it that Demonic Tutor is cheaper to cast but like…why would that make it a game changer and not Diabolic Tutor.