Unholy Presence gives a Frost DK more:
Damage since you can run faster to the enemy.
More Heals by running and bandaging people.
More Runes by regenerating them faster so you can Death Strike more
Stacks with Death's Advance to give you even faster speed for bandaging
Frost Presence gives you:
Frost is clearly a hybrid spec designed to frost the abilities of your team through damage, bandaging, and frosting. If you just want damage, I hear that Fury warriors are better now.
Me, I'll stick to my 60% damage 40% bandage hybrid buffer that when combined with two other classes can take down 5 or 6 dedicated primary classes easily.
Or you can ignore me, not test things for yourself, and sheep with the crowd
I like you