What is the Ideal size of smartphone screen according to you?

According to me this is really a big hurdle as it becomes completely difficult (not impossible) to handle such large so called smartphones/phablets

I think HTC’s 4.7″ seems more than perfect because for my 4.5″ suffices, though then I won’t get the phone with best of best specs if one has to choose from smaller inches. Though at moment I’m in complete awe of HTC ONE