Shawn Blanc perfectly sums up, in his review of Clear, why I am using both Clear and OmniFocus on my iPhone:
But the biggest caveat with OmniFocus is its speed. It takes more than a few seconds to launch the iPhone app and enter something in. New OmniFocus items beg to be given contexts, projects, start dates, and due dates. While this is OmniFocus’s greatest strength, but there are moments when this is also OmniFocus’s greatest weakness.
I love OmniFocus and if forced to pick between Clear and OmniFocus, the latter will win every time — no hesitation. Luckily I don’t have to choose one or the other.