The vulture's certainly better and fits with the Carrion, though for me the number one choice as an alternative model is the Khemric Titan/giant Scarab statue. I far and away prefer the Tomb Kings using statues over reanimated monster corpses (which is a much more a Vampire Counts thing). Indeed it fits the lore better in my eye too - the Tomb Kings hate being Undead and they never wanted to be Undead in the first place, so it appears hypocritical if they force that servitude upon the corpses of other creatures as well (whereas Vampires and Necromancers of course have no qualms in doing so for humans or larger creatures, having sought the gifts of Undeath willingly). By contrast, the animated statues are a relic of the wars fought by the Tomb Kings when they were human against Nagash's legions of Undead, so naturally the ancient magicks within those statues are still programming them to fight alongside their masters, whether they are living or Undead, and their original success against the Great Necromancer's armies would naturally present them as a trusted source of durable allies to the Tomb Kings.