It may be the only one that doesn't require a vampire, but it's not necessarily the one that does the most for deathrattle units if you're willing to compromise by sprinkling a vampire or two in. That's more Legion of Blood, or maybe Vyrkos.
Still, my sympathies are with Legion of Night as well, at least to start. In the long term I'll probably get stuff to run all of the factions. Mostly just based on Mannfred's new rules looking fun. That and I like necromancers, and the LoN claw artefact is the best support for necros that any of these subfactions offer.
That said, though, Mannfred at least mostly does his own thing regardless of which faction you field him in, and the faction has so many alternate deployment options that the cool LoN outflanking gimmick really doesn't add up to much. Vargheists deep strike anyway, any of our summonable stuff can deploy via gravesites - which no longer requires a nearby hero, Vyrkos can summon wolves, the Anvil of Blood has the absolutely absurd "Arise, My Legions" or whatever-it's-called command ability if you're a bad enough sport to use it and your opponent is fool enough to agree to it. And +1 armor on the first turn only, while not nothing, isn't a lot either. Especially if 3e rolls around and says it can't stack with grave guard shields.
I'll still be starting off with a hodge podge, one of everything type Legion of Night list, figure out which units I like, and then look to get more of those units while shifting to a bloodline that better supports them specifically. Maybe blood knights and dragon lords in Kastelai. Maybe zombies, dire wolves, and Volga in Vyrkos. Maybe coven thrones and grave guard in LoBlood. Maybe Avengori monster mash - to be honest that one probably appeals to me the least, but I would be able to build up the pieces of a more exciting Gristlegore FEC version of the army at the same time.