We just took the three phones out together. The wife still has a 5s, my 6s plus and the moto x style. There may be a slight difference in the 5s and 6s plus but not enough to matter. Both are really bad in Direct Sunlight. The moto x style is excellent, I can use it in DS as easy as I can in the shade. I prefer the screen and shape of the moto but ios meshes better with my mac and ipad so it's going to one of the (grown) kids.
We live at 9000 feet so the sun is particularly harsh and sunburn comes quick if that makes a diffence.