So I've compared my 5S and 6+ side by side by pressing the home button twice on both phones at the same time to see which device will get to the multitask screen, it turned out that my 5S is about 1/3 sec faster than my 6+. Both devices has the same of everything (amount of apps, # of apps opened, photos, music... etc.). I can definitely feel the delay on my 6+. 
