I've tried both Omnifocus and Things, along with several To Do apps that have since shuttered (Wunderlist, Producteev, and Astrid). I loved Astrid and was sad when it was acquired by Yahoo and then almost immediately shut down.

However, the to do app I keep coming back to is ToDoist. That's not to say that there are not other amazing ones. I think choosing productivity apps definitely comes down to personal preferences.