Darling has been very good, but look at the big bodied support he gets on the West Coast forward line - Kennedy, Lynch and then throw in Nic Nat and Big Cox when resting down there. He is often matched up on a smaller, lighter defender, in our forward line he would attract a Glass or Rutten type.
Darling is already physically mature, Cook isn't. As with all drafting comparisons you need to wait a few seasons to see how the players develop.