As mentioned in post three. The top advantage is the ecosystem. The iPhone will work pretty seamless with your MacBook Pros. The OS gets updated at a pretty frequent rate. Straight forward and simple to use.
I would also suggest with it being so close to September/October (if you end up deciding on jumping to the iPhone) to hold out for the new 6s or 6s+. It will have double the ram of the current 6/6+, also rumoured to have a jump from 8 to 12mp camera (possible 4k video recording) and a brand new feature of ForceTouch (same tech used in Apple Watch and new trackpads in the retina MacBook and 2015 MacBook pros.)