For me, 5.5-5.7 inch is the best. More than 5.7 inch makes the phone bulky and difficult  to use with one hand.

Before the Pro 5 i had a 4,7" phone. I said don't need bigger, but max 5" what is comfortable to me. Still i took my chance with a pretty big screen and now i say don't want any lesser than 5,5". Yes, below 5,2" is more comfortable for one handed use and keeping it in the pocket.
However the truth is, for me, 4,3" is the best for one handed use, sometimes it was hard even with 4,7". Most things i can manage with the Pro 5 too, but i just got used to both hands if needed and as they say bigger is better. After 5,7",  4,7" is painfully small, it is just not comfotable to surf the net, watch movies, play games or doing any serious content consumption. It is way more uncomfortable than using both my hands or adjusting the position a little in the pocket.
Still, 5,7" is truly the maximum size for me or more precisely the size of the Pro 5 is the max i still can handle. But bigger the screen to body ratio the better.

Again compare android and windows..Also please donot use example of Microsoft..Also their low quality marketing way decrease market share from 2.5% to 0.7% in first quarter of 2015..And also microsoft stop working in smartphones...

5.2 and below best option for all use to use..easy to one hand operation,fits pocket easyly..My  opinion 4.5-4.7 best full compact....And if need big screen go for tablet why you need a big screen mobile with bezels..??saving Battery also helpfull in 4.5-4.7inche device..

Also 5-4.7'' phone would be enough for all of our daily task still now...

5.2 is perfect mobile  size

5.2" and above is better!!!

Check complete information.  Microsoft stops working on Lumia
Because they are working in premium which you might not able to afford

Surface phone series.  

Like Microsoft Premium surface book,  and Surface pro 4  :  which won all awards from design,  hardware and performance award

5,2 perfecto

5,2