I currently have a Galaxy S5 and man is 5.5'' the worst size. It's always either too large or too small for what I am doing. When watching gaming videos I can't read the UIs and when doing general tasks it's too bulky. I would prefer just having a 6''+ phone or in having a smaller phone and a tablet. My mother has an iphone and I think that's a good size for a smartphone. I wouldn't go any smaller than 3.5'' for sure as I do at least want to read websites and blogs as well as be able to easily read my emails on the go.