Jaya Ballard, Task Mage
Tap, R , Discard a card: Destroy target blue permanent.
1R, Tap, Discard a card: Jaya Ballard, Task Mage deals 3 damage to target creature or player. A creature dealt damage this way can't be regenerated this turn.
5RR, Tap, Discard a card: Jaya Ballard deals 6 damage to each creature and each player.
Sengir Nosferatu 3BB
Creature - Vampire
Flying
1B, Remove Sengir Nosferatu from the game: Put a 1/2 black Bat creature token with flying into play. It has ", Sacrifice this creature: Return to play under its owner's control a card named Sengir Nosferatu that's removed from the game."
lets take out wrath of god and sudden death out of the picture when comparing Sengir Nosferatu and Seketal Vampire, since they both die to that.
Sengir can dodge spells that targets, while Seketal can sustain spells that does not prohibit its regeneration ability.
Assume you got enough mana to use both Sengir and Skeletal's ability for many times and given we are talking about the new type2.
Sengir could dodge spells from no-regen burn to -x/-x to condemn and condem variants, to fetters and to bounce, while Skeletal has no immunity against those.
On the other hand, Skeletal Vampire has more power and more combat harden. As many of you know, it generate bats, so it can slowly build up an army, but Sengir is only one creature. Thus, Skeletal is better against taking aggro and finish a game faster. Since it regenerates, it can survive Edict variants and Wrath of God variants ( sunscour, hour of reckoning despite no one play them), which Segir does not. Upon death/leaving play, Skeletal can leave a small army of bats. Sengir, however, is one creature, so when its gone its completely removed.
If your want more resistance against opponents creatures and edicts as wells a power, skeletal is your buddy. On the other hand, Sengir would do better saving itself from spells that Skeletals cannot survive.