Necropolis or Castle (Which one is stronger?)

Griffons don't have a counterattack; you're confusing it with endless retaliation. Yes, Necromancers are weak at level 7, but at level 6 with 2 damage... Vampires with regeneration, Ghouls with a gas cloud, and Spirits are annoying, and if Zombies manage to reach you, they can't be underestimated, plus the Legions of Bones. I'm voting for Necromancers.