Protector of the Crown Having and maintaining the monarch can be very important for certain decks, and Protector of the Crown makes it easier to keep the title
First, Nights Whisper has a more forgiving mana cost
But bloody hell when did some of these cards get so expensive

Anywhoos - here's the quick run-down of all the new cards - White (8) : Act of Authority, Angel of Finality, Curse of the Forsaken, Darksteel Mutation, Mystic Barrier, Serene Master, Tempt with Glory, Unexpectedly Absent Blue (8) : Curse of Inertia, Diviner Spirit, Djinn of Infinite Deceits, Illusionist's Gambit, Order of Succession, Tempt with Reflections, Tidal Force, True-Name Nemesis Black (8) : Baleful Force, Curse of Shallow Graves, Fell Shepherd, Hooded Horror, Ophiomancer, Price of Knowledge, Tempt with Immortality, Toxic Deluge Red (7) : Curse of Chaos, From the Ashes, Sudden Demise, Tempt with Vengeance, Terra Ravager, Widespread Panic, Witch Hunt Green (7) : Bane of Progress, Curse of Predation, Naya Soulbeast, Primal Vigor, Restore, Spawning Grounds, Tempt with Discovery Multicolor (10) : Derevi, Empyrial Tactician, Gahiji, Honored One, Jeleva, Nephalia's Scourge, Marath, Will of the Wild, Nekusar, the Mindrazer, Oloro, Ageless Ascetic, Prossh, Skyraider of Kher, Roon of the Hidden Realm, Shattergang Brothers, Sydri, Galvanic Genius Artifact (2) : Eye of Doom, Surveyor's Scope Land (1) : Opal Palace ~

Also note that his -X can be used immediately, or later, to take out planewalkers or dorks early, using his high loyalty for good effect