Too big
6.4 inches is just too big for a phone. Yes it's great having a big screen for watching media and web surfing, but as a device to carry with you all day it's impractical. The screen on my OnePlus 3T cracked recently from being in my trousers pocket, which is uncomfortable in the first place. I now find myself having to pick tops with pockets just to carry the damn phone - and that's merely got a 5.5" screen