A ghost ring sight is an aperature sight! It's just that the aperature (hole) is larger in the ghost ring than most people associate with an aperature (peep) sight. The ghost ring comes with a choice of two size holes to use.
The ghost ring is generally considered a little faster sight to get on a moving target with, but by taking the screw in part out of the standard aperature, there really isn't much difference.
I would prefer the standard aperature, a good Williams, Refield or Lyman, with their more precise adjustments, on the 30-30 Marlin.