From a gameplay perspective Spellcasters (or as I'm going to keep calling them, Witches) are just so powerful with what they have. While Vampires... Feels like you need to bite someone every 5 hours and plasma packs are nowhere near as good as they were in TS3, though it is nice having to not deal with sleeping at all when you avoid using powers or the sun! Sadly with witches though, things like infernate don't feel as good as they should seeing it still gives your Sim the overwhelming urge to panic at the fire they've caused. I just want to burn a few Sims here and there!
Feels like witches get a little less to do though, there's Magic duels, there's buying a wand or two, there's casting a few spells... And thats what I could expect. While vampires have a fair bit, from breaking into houses, biting people because you can and outright trying to cure them. Having a few quirks to pick from adds to the uniqueness of each Vampire too. Not so much with the Witch because of the lack of quirks, only so many ways to make each one unique when they all can learn the same magic!
Witches lose points for not having their classic pointed hats without mods though.
I like to settle with mods to allow hybrids to function properly, just as they could in the Sims 2. Witch-Vamps are a fun mix I'll never live without. All the fun without the sun while just being able to break into a house at will, take everything of value and torch the residents, works so nicely with the co-operation of a Witches spellset!
I still feel like witches would be even better if they had some sort of Sims 2 styled allignement, have evil witches be much less into the whole practical magic, and more into the "ruin your life while cackling like a maniac" magic. At least the vampires don't have to ask to bite anyone anymore...