Necropolis or Castle (Which one is stronger?)

In my opinion, it's better to play as Necropolis, although there's only one archer unit, and even that one is high-level, so you won't get it right away. At first, it might be a bit inconvenient, but later on, it doesn't matter – a well-managed army of skeletons, zombies, ghosts, and vampire lords can achieve great things. :)

P.S. The Castle is also good; again, it all depends on the player. :)