I prefer Vampires. I love them. Their powers, dark form, Forgotten Hollow and everything about the Vampires in TS4.
I haven't played that much with Aliens in TS4. I'm actually planning to remake
Pollination Tech#9 Smith and his very big and weird family from The Sims 2.
I do have one question about Aliens tho:
If I give Alien a human form will they use that disguise or their Alien form when I'm not playing with the family and my Sims meet them out at the town(at the gym, restaurant, spa etc)?(I play rotationally with many families)