What kind of castles do you choose?

I can't see the use of these 10 Admin Forts. Sloth 3 is more attractive than a 10 Admin Fort that will provide me, more or less, the same production value and gold loss AFAIK.

I remember playing my first few games of the Demo and attempting to field any sort of army with the default tower and feeling like a complete idiot later when I changed it up to a Castle or Wiz Tower.