The problem with the iPhone 6 dispaly

Text rendering. Unless iOS 8 fixes this, then even a higher-res 5in display won't be much more legible. This problem may be compounded since my understanding is that current rumors put the iPhone 6 display well below the 445ppi of current-gen 5in displays.

How iPhone renders text compared to Android:

Image and video hosting by TinyPicImage and video hosting by TinyPic