I don't think you can go wrong with either Johnson or Didak.
If you want slightly more consistency, go with Didak, as he runs through the middle.
On the other hand Johnson is more likely to kick bigger bags of goals, as he plays closer to goal, but this can affect his consistency.
Forget about Murphy.
My dilemma is who to cut: Hall or Ziebell?
I got exactly the same dilema this week. Im cuting Ziebel. He has the pies this week and cant see him gaining much. Hall has melbourne and has shown more promise. With that being said if hall stinks it this week he will be gone next week