I'm digging the durabitilty of the Z2 with its dust/water resistance. I work in the elements, and it's a must-have for me.
My bro has dbrand's carbon fiber skin on his S4 and it really makes that somewhat plastic-y device really look amazing!
Definitely the separate buttons for video and still photos in the camera app! I've got a 4yo and catching the action on my iPhone5 is an exercise in futility sometimes because the mode switching has such a significant delay.