Vampires are a significantly more powerful lifestate, I have compared a Fully-Perked Virtuoso Spellcaster with every Spell Learned to a Fully-Perked and Optimized Grandmaster Vampire and here is what I have discovered.
- A fully-perked/optimized Vampire is immune to up to 11 Death Types which include Drowning, Starvation, Freezing, Overheating, Pufferfish, Steam and Old Age, even emotional Death's if they take the perk which grants them Deadened Emotions, they can become immune to Sunlight MEANWHILE a Fully-Perked Spellcaster is immune to only 1 Death Type which is Old Age, when Seasons are installed it becomes quite obvious how vulnerable their lifestate is compared to that a of a Vampire given they will Freeze and Overheat as easily as any normal Sim, they can "Cheat Death" with the Potion of Prompt Resurrection however it only lasts for 2 days, from what I can tell the Spellcaster has the inferior form of Immortality, the Potion of Immortality only stops them from dying of old-age, it does not actually give them eternal youth, you need the Potion of Rejuvenation for that and from what I hear it only resets your current age so if you do not want to age up you need to keep taking it.
- A fully-perked/optimized Vampire only has 2 needs which are Thirst and Vampire Energy, the former can be ignored with the Tamed Thirst perk as lack of thirst will not kill them, Vampire Energy is just their magic meter and is nothing like regular Energy, a Vampire with no Vampire Energy will not pass-out, they will just act all sluggish but they can restore it very quickly by performing Dark Meditation MEANWHILE a Spellcaster still retains their regular Human needs, they still need to Bathe, they still need to use the toilet, they still need to socialize or have Fun.
- Power-Wise their power-sets are very Similar, both have a few powers the other can not do but ultimately what is more useful? Move as a Bat or Fly on a Broom? from what my experience has told me the Witch will always go outside before using the Broom where as the Vampire will become a Bat wherever, this means their method of traveling is much quicker, the animation may also be shorter which means Bat Form is superior to Flying on a Broom, as for Mistform and the Spellcaster's Teleportation, spell they are mostly equal, it has also come to my attention the Vampire power-set has the capability of actually killing other-sims as their ability to bend emotions exceeds that of what the Spell-caster has available, remember the Grandmaster ability that gives all surrounding Sims an 8+ emotional debuff? other powers like Morphiate may be fun to use but ultimately they have no real purpose, making a Sim soil their pants however...