If pushed....
Doom kills Vast on scope, albums, tracks, collabos etc and has his own language. Shit like Madvillainy is timeless. Vast kills punchlines and has the most presence in an mc ever. I prefer Vast Aire's flashiness, one liners and charisma but just can't say he's doper than Doom. Yet.
The difference is that Vast is a (sometimes blunted and incoherent) Titan and Doom is an (also often blunted and incoherent) Institution.
I cannot think about such things when I should be out putting food in my fridge. This is an evil, meaningless yet enticing conundrum for a Monday.