Zed or Darius?

Ive been saving up for a 6300 Champion for a while and i was considering getting or with that IP. But i really cant decide which one to get, with i will go and stay with Top lane and i had some experience when he was free. When it comes to i will get to try something new and test out mid lane. I'm really trying to figure out which i should get and i keep waffling back and forth