My vote would be for the Apple silicone case, but I'm biased and it's the only one of the six that I've personally tried. That said, it's the best phone case I've ever used -- nice soft-touch, grippy material and I believe the edges of the case come up enough over the curves of the front of the phone to make it nearly impossible for the display to hit the ground if you drop the phone on a completely flat surface.
Although the bottom looks susceptible, the bottom corners of the case stick up enough that they'd probably hit the ground first.
With Apple's return policy, trying it is a pretty safe option.