What made you go back to the 5s?
I have both phones....and at this point in time I really prefer the nexus 5. It has addressed all the weaknesses I used to see in android compared to iphone.
The screen is extremely accurate in color reproduction, nothing crazy saturated like other android phones. Plus...the screen size is perfect.
The touch input lag seems to have been addressed here, and is something I have read reviews regarding. It is every bit as responsive as my 5s to touch.
The speed of the phone and smoothness of the system is on par with the 5s, and rivals the 5s in some areas.
The camera is good. The iphone 5s captures good photos, but it over exposes some shots. The HDR+ on the nexus 5 takes the best photos I have seen from a smart phone.
Battery life is comparable to the 5s.
Updates are guaranteed.
Productivity is much higher on this phone, largely due to integration from google.
Can't really think of something that the iphone 5s is exceedingly better at, though I have been trying to....